* Add arrowhead support

As described in TODO, dotparser.js does not support 'arrowhead'
attribubte of edge.
This update is for adding 'dot' and 'tee'(bar) styles.

* Add example for arrow styles

* Add box arrowhead

To support box arrowhead of graphviz, add Box endpoint class in
EndPoints.js and box attribute in dotparser.js.

* Add diamond arrowhead

To support diamond arrowhead of graphviz, add Diamond endpoint
class in EndPoints.js and diamond attribute in dotparser.js.

* Add crow arrowhead

To support crow arrowhead of graphviz, add Crow endpoint
class in EndPoints.js and crow attribute in dotparser.js.

* Add normal arrowhead

To support normal arrowhead of graphviz, add Triangle endpoint
class in EndPoints.js and normal attribute in dotparser.js.

* Add curve arrowhead

To support curve arrowhead of graphviz, add Curve endpoint
class in EndPoints.js and curve attribute in dotparser.js.

* Add inverted curve arrowhead

To support inverted curve arrowhead of graphviz, add InvertedCurve
endpoint class in EndPoints.js and icurve attribute in
dotparser.js.

* Add vee arrowhead

To support vee arrowhead of graphviz, add Vee endpoint class in
EndPoints.js and vee attribute in dotparser.js.

* Add arrowhead examples

* Fix bug for accessing null attribute

In createEdge(), accessing 'attr' causes an error if the edge has no
attribute and the value is null.
This update fixes bug for accessing null 'attr'.

* Update description for arrows.to.type option

Add followingn options for 'arrows.to.type'.

* box
* crow
* curve
* diamond
* inv_curve
* triangle
* inv_triangle
* vee

* Update edgeStyle example for arrow types

Add arrow types for the example.

'box', 'crow', 'curve', 'inv_curve', 'diamond', 'triangle',
'inv_triangle', 'vee'

* background docs
* edge background
* Update edges.html
* Update EdgeBase.js

* Interim save cleanup typedefs

* Completed transferral of *the* big typedef

* Transferred all typedefs to typedefs.js

* Small refactoring in Label._drawBackground()

* Added size calculation to Label, basic framework for detecting click on label.

* First fully working version of label click.

* Put in extra checks, refactored visibility of labels for more general usage.

* Final fixes to code; added to example and in docs

* Adressed review comments

* Add next attempt to fix Travis unit test bug

* Addressed review issues

* Add endpoint 'bar' to Network

Fixes #3412

- Adds class `Bar` and handling to `EndPoints.js`
- Adjusted `options.js` for endpoint, minor code changes
- Added to example `network/edgeTypes/arrowTypes`.
- Added to edges documentation

* Grumbl fix travis unit test yet again. Go die already!

* Moved endpoint-specific code to module EndPoints

* Further decomposed functionality for endpoints

* Added commenting, notably for typedef's

* Add next attempt at fixing travis bug

* Corrects usage of @static jsdoc annotation

* Correct unresolvable types

* Correct types in jsdoc and remove extraneous @class & @constructor jsdoc

* Remove incorrect @static jsdoc

* Adds missing jsdoc for param copyFromGlobals

* correct jsdoc in util

* Corrects casing on jsdocs

* Swaps @inheritDoc to @ignore for constructors where constructor args are documented in the class

* Instantiates Errors with `new`

* Addresses improperly defined @callback tags.

* Split callbacks out to separate jsdoc

* Moves constructor jsdocs back to constructor and drop @ignore.

* Enables require MethodDefinition for require-jsdoc lint rule and corrects 66% of missing Method Definitions

* Adds jsdoc for all remaining methods and corrects @class/@constructor documentation

* Define values more accurately

* Correct bugs that prevent jsdoc generation

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

* Corrects lint violations

* 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

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.

* self reference edge should now appear in all cases
* add checks for shape width being NaN to get correct circle data
* reorder resize arguments in Diamond, Dot and Star

* element characteristic changes
* assume edge color inheritance is correct before choosing
* Adjust nodes’ chosen’s boolean -> bool
* Need to get user-reset size
* make example edges thicker for more noticeable shadow
* preemptive ES6 fix (see #2500/#2501)
* documentation for the feature that was previously overwritten

see #1608

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