* Network: Add extra check on null value during label handling

This fixes an oversight in #3486. Unit tests added, not only for null labels, but for all weird label values I could thing of.

* Enhanced unit tests, adjusted label check

* 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

* 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.

* Added commenting for options, refactored choosify()

* Refactored updateLabelModule()

* added comment at node creation

* Completed fix for #3350

* parseOptions() different handling for bridged/extended; unit tests for reversal of options

* Fixes on linting and unit testing