* First interim commit

* Fixes during testing

* Allow multiple edges to be hidden by a clustered edge.

Fix for #3245.

This fix adjusts the clustering edges so that theyi can refer to multiple edges instead of just one.

This API method is now insufficient, since multiple base edges can be returned.

- Added replacing method `clustering.getBaseEdges()`
- Adjusted example `changingClusteredEdgeNodes` for the new method. This is the *only* place where `getBaseEdge()` was used
- Adjusted documentation for new method and deprecation old method.

Method `getbaseEdge()` should now be considered `deprecated`, and in due time should be removed.

* Edits of method name in example

* Edits of method name in example

* adjusted deprecation method getBaseEdge() in docs

* Adjusted deprecation method for getBaseEdge() in docs

Fix for #1222.

This makes the passed data of events `hoverNode`, `hoverEdge`, `blurNode` and `blurEdge`
more conformant to the passed data of the click events. In particular, the following
fields are added to the event data:

```
event: [Object] original hover event,
pointer: {
    DOM: {x:pointer_x, y:pointer_y},
    canvas: {x:canvas_x, y:canvas_y}
}
```

The changes can be tested with example `network/events/InteractionEvents`.

* Added unit test for Validator, minimum viable version.

* Added test-console to package list

* Completed minimum viable unit test for Validator

* Added Validator unit test for explicit 'undefined'

* Added commenting for better understanding

* Refactored specific heirarchy fields to HierarchyStatus; more commenting.

* Small edits to LayoutEngine

Fix for #3164

- `network.clustering.cluster()` now handles all nodes, not just the visible ones
- Changing ivisibility of nodes now explicitly takes clustering into account, see `Network._updateVisibleIndices()`
- `network.clustering` does not change `hidden` status any more.

The important part of this PR is the realization that 'hidden' and 'clustered' are two distinct things and should be handled separately.
In particular, clustering should **not** change the `hidden` state in any way.

**Note:** This is a small fix and should be easy to review.

Second fix for #3251.

In method `DataGroup.initializeData()`, if the passed `rawData` is bad for some reason,
it was possible to lose the subscriptions due to early return from the method.

This fix changes the order in the method so that the guard clauses execute *before* the
subscription is changed.

**Note: ** This is a simple fix and should be easy to review.

Fix for #2579

- Adjusted node title definition in `options.js` to allow DOM elements
- Changed `BridgeObject()` in `util.js` so that DOM elements are *not* bridged.

* Bidirectional scrolling.
Make horizontalScroll and verticalScroll work together.

* Fix delta variable declaration

Using ?: operator

* Remove notice about vertical and horizontal scroll conflict

There is no sense considering #3162

Fix for #2856

- Toolbar gets reshown when cancelling edit node dialog
- No shadow displayed upon save in edit node dialog

The latter is actually a more general problem. Function `mergeOptions` in `util.js`
made an assumption as to the correct value of field `enabled`. It now takes the value
from `globalOptions`, if present.

* First working version of eslint enabled with gulp

* Tryout of eslint with graph3d files

* Cleanup of gulp and eslint files.

* Completed test by linting graph3d

* Disable travis linting for now

* Remove global cmd param from .travis.yml

* Fix missing reference to Graph3D instance in DataGroup

Fix for #3251

A reference was missed in DataGroup.reload() during refactoring.
Rather than fix this method, it has been removed and the logic moved to `Graph3d`.
This makes for somewhat cleaner code.

* Fixes due to review

* Add C++11 and canvas module for travis tests

* Added libgif, updated version gulp-clean-css

* Update version webpack

* Force versions minimatch, graceful-fs; fixes for upgraded webpack

* Force version minimatch through travis.yml

* Fix comma's in json

* Add extraneous modules to package.json; final attempt at forcing versions of minimatch and graceful-fs

* Final changes module versions

* Fix due to linting

* Fix typo in package.json

* Upgrade eslint

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* created a checklist for the release process

* unchecked everything

* added make github release

* Fix colliding subgroups when having same end-start times

* Remove npm-debug logs

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* created a checklist for the release process

* unchecked everything

* added make github release

* Remove npm-debug logs

* Fix setOptions restack when setting stack

* Remove extra line

* Fix comments from review

* Set dimensions properly of images on initialization.

Fix for #3203

Image nodes were assigned the default size on initialization, leading to very compressed images.
This fix adjusts the default size as soon as the images used have been loaded.

The approach for dealing with this has been adapted from `CircularImage`.

* Fixed tabs

* Consolidated common code for drawing in nodes

* Consolidated updateBoundingBox(), default version

* Setting bounding box margin in separate method

Fixes a race condition that set an item's group to be set to undefined
if it was dropped and then dragged again without a redraw happening in
between.

The returned node id's were exactly the wrong way around;
'to' returned the parents, 'from' returned the children.

This fix swaps the tests for determining which to return.

* Fix for timeline TimeStep.roundToMinor - resolving issue #3105

* Adding some tests for TimeStep

Code in the `_line()` of the sibling Bezier edge types was either extremely similar or identical.
The Bezier drawing code has been consolidated in a single method in the parent class.

This method is needlessly complicated. Code has been adjusted to better show the intent.

In addition:
- reuse of variables already present, notably `dx` and `dy`
- put recurring code fragments into local variables
- removed second conditions in constructs of the form `if (condition) ... else if (!conditioni) ...`

The refactoring can be taken further, but it would change the conditional flow, which would complicate reviewing.
The current changes highlight the similarities between the code blocks.

* Consolidate code for determining the pixel ratio

* - Removed local param  'pixerRatio' from CanvasRenderer. Now only canvas.pixelRatio is used.
- consolidated ctx.transform() calls in Canvas
- Added/edited commenting (also TODO's)
- Added Canvas.getContext()

Fix for #3036

Option `smooth.type: dynamic` is not allowed for hierarchical layouts.
This was handled properly for the main options, but not for the node-specific options.

Options within node instances arei now checked for `smooth.type: dynamic` and replaced
by `horizontal` or `vertical`. The implementation adds listener `_adjustEdgesForHierarchicalLayout`
in `LayoutHandler`. This listener must be activated every time noder- specific options might change.
This happens in the logical places within `EdgeHandler`.

* clusters in hierarchical working for sortorder 'hubsize'

* Code cleanup

* Protect Network from zero and negative mass values

Fix for #3133

Option-field 'node.mass` must be >= 0.
Checks have been added at the nodes level, for both nodes-global and nodes specific options.
In addition, an internal check has been added for `NodeHandler.defaultOptions`.

The documentation has been adjusted for this change.

* Fix whitespace

* Prevent crashes from invalid id's in `Clustering.findNode()`

Fix for #3163

- Added safeguards in said method, to prevent exceptions happening when invalid id's are passed in.
- Adjusted documentation for said method
- Added notes to flag unused methods in `Clustering.js`

* Removed incorrect NOTE-comments from methods that are indeed used

Fix for #3106

Event `stabilizationProgress` is now always sent for iteration 0 and for the very last stabilization iteration.

* First working version of new class DataGroup.

* Adjustments for review - done all points except last

* DRY distinct values, clean up sort code

* Added missing @param's to comments in DataGroup

Call on issue brought to light by #2990.

`ctx` should not be passed as a parameter to the call - not needed and not conform to documentation.
Also cleaned up the calling code to remove the double `fontOptions.chooser()` call.

* Properly handle newline escape sequences in strings for DOT

* Adjust comments in code

* First save after refactoring

* Fixes after testing

* Final changes

Currently `align` is only available as a global timeline configuration
option. This change allows overriding alignment on a per-item basis.

* Fix selection nodes so that option selectConnectedEdges works as expected

* Using instance var select instead of local var in Edge.drawLabel()

* Changed order of (de)select events for network

* Fixed parameters to _generateClickEvent() to be compatible with previous.

* Added param 'direction' to Network.getConnectedNodes()

* Redo commit - Network.js does not need to change

Awesome work! Thanks again!

* Add support for multiple class names in utils add/remove class methods.
Reset subgroup heights in resetSubgroups method.

* Adjust to better process class names

* Add 'showTooltips' timeline option

* Only show timeline popup if option showTooltips is true

* Add 'showTooltips' option to timeline docs

* Add tooltips disabled timeline example

* Fix redraw order

* Fix error when option is not defined

* Allow template labels

* Add .travis.yml file

* Add experiment travis code

* Fix react example

* Improve redraw performance by not restacking non-visible groups (related to #2835)

* only restack necessary groups on redraw (related to #2835)

* replacing all ES6 imports with CJS require calls
resolves #2934
used the following regex to apply the changes in lib:
s/import\s+(\w+)\s+from\s+(.*);\s*$/var $1 = require($2).default;/
s/import\s+(\w+)\s+from\s+(.*)\s*$/var $1 = require($2).default;/

* cleaning up inconsistencies

* Add warnings and errors for image loading

* Fixes and commenting for image loading

* Fix typo

* Small fixes due to review

Sorry for the delay on this... It took me a while to confirm this PR again. I don;t know why I didn't merge it at the time I reviewed it. Looks great to me!