* Docs : fixes and enhancements for the documentation template.

This is an evolutionary update for the `jsdoc` document generation.

- Added functionality to retrieval of data comments
- Added partial for generating documentation in the method tables.
- Moved commenting to source for `Network#clusterOutliers`. This was used as a case example.

- Adjustment to CSS to get the decription text margins same as original
- Added step to generate documentation to release checklist
- Fixed some commenting which `jsdoc` couldn't handle

* Fixes for linting

* Add template for document generation with 'jsdoc'.

In essence, it defines the subdirectory `docs` as a `jsdoc` template. Benefits:

- allows the usage of partials, in order to DRY common parts of the html files.
- makes available the jsdoc-comments, for addition into the documentation.
- enables extraction of data from the source code. For example, the list of edge endpoints `['arrow', 'bar', 'circle']` can now be extracted from the source and inserted into the documentation on generation.

In this initial version, the only file that has been changed is `docs/data/dataset.html`.
In here, partials have been added to illustrate how common page elements can be DRY'd.

The template has been set up in such a way, that resource files will be copied and that html files can pass through unchanged if no special template tags (`<?js...?>`) are used. This allows for a gradual transition of the html files to templates.

**Usage:**  `gulp docs`

- The result files are placed in subdirectory `gen/docs/`.

**NOTE:** The release procedure will have to be adjusted by adding this gulp command.
The docs-files will then have to be taken from `gen/docs`.

* Edits to docs/README

* Adjusted layout of README.md

* Further edits to README.md

* Removed pre tags again in  README.md - don't work in code block

* Linted the gulpfile

* Added proof of concept for docs generation from source

* Network: preload images in options for all shape types

Fixes #3532

If the images option is set, preload it, even if the node shape is not `image` or `circularImage`.
This needs to be done because the user can switch to an image shape later, as is happening in the issue.
Option `image` is only mandatory for the image shapes.

There is no unit test for this, because it would need a mock object for Image and I didn't succeed in creating/finding one.

* Network: Handle null data gracefully

During testing I discovered that passing `null` for network data leads to a thrown error.
This adds a guard to prevent it, plus unit tests for regression.

* Added unit test for Array.prototype mangling - first passing version

* Enhanced unit test for prototype stressing to catch more illegal for-in loops

* Fixed all for-in linting violations

* Removes redundant .eslintrc from graph3d, lints the rest of the code base, and enables valid-jsdoc lint rule

* Corrects lint violations

* First working version of updating clustered edge

* Added fix for #1315 as well

* Enable unit testing for module Network

Adds mocks for certain components, in order to let module `Network` be run in unit tests.

Changes:

- Create a mock object for `hammer.js` when running browserless. The inspiration is taken from [here](https://github.com/uber/deck.gl/pull/658)
- Create a mock function for `window.requestAnimationFrame()` when running browserless in `network/modules/CanvasRenderer.js`
- Added unit test for `Network` to show that unit testing for it now works
- Fixed naming of container in `test/Graph3d.test.js`

Since `hammer.js` is also used in other modules, this fix is potentially an enabler for full-module unit tests for those as well.

* Cleanup unit test Network

* Added unit test for fix issue #1218

* Adding test for #1315 - Interim save

* Completed unit test and fixes for #1315

* Added fixes for #1291

* Added unit test for #1219

* Added header comment for Clustering.js, small fixes

* Fix for unit test

* Added example networks to unit test

* Fix error in loading disassemblerExample

* Network unit test final fixes

* Fixes for linting

* Fixed essential typo

* Fixed linting error

* Fixed unit test

* Fixed unit test again

This PR contains two small fixes to ensure that all examples rung.
I noticed that some examples weren't working, so I tested them all.

* Makes network eslint compliant
Unused variables in private functions, who were never called internally with those arguments were removed.
lint rule was disabled for public functions, and in private functions which were called internally with those unused arguments

* Disables linting for unused args passed into DataSet and DataView

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.

* clusters in hierarchical working for sortorder 'hubsize'

* Code cleanup

* 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

added example. Improved handling of options for hierarchical view.

- Fixed #1528, #1278, avoided ID's being cast to string for methods that return ID's as well as storePositions casting to string.

Missed "apply" call on DOMtoCanvas call

- Added beginnings of unit testing for network.