* 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

This is the next escalation on the war against the Travis unit tests failing (which came into being by yours truly).
By accident, I could recreate the unit test failure on my development machine. This led to a more directed effort to
squash the bug.

The insight here is that test `(window === undefined)` fails, but `(typeof window === 'undefined`)` succeeds. This undoubtedly has to do with the special status `window` has as a global object.

Changes:

- Added check on presence of `window` in `Canvas._requestNextFrame()`, fixed local source errors.
- Added catch clause in `CanvasRendered._determinePixelRatio()`
- small fix: raised timeout for the network `worldCup2014` unit test

* 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

* 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()

* Should fix issue #2100 and fix another issue we discovered around clusterByConnection leaving phantom edges.
* fixed a wrong variable name
* fixed DataView.test.js assert
* Update Canvas.js
* remove whitespace; remove end of file newline on Canvas.js
* strip end of file newlines
* fixed styling. spacing, semicolons, line length

- Accepted pull request #1544, thanks @felixhayashi!
- Fixed documented bug in #1544.

- unified some methods in the networkUtil
- Fixed initial zoom issues #1252