* Network: Adjust documentation for arrows.middle.scaleFactor

Addendum to #3474.

Updated the documentation, so that users can know about flipping the middle arrow with a negative scale factor.

* Adjusted text for review

* 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!

* 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

* Multifont node and edge labels
* adjust documentation
* rework mod-font property inheritance
* Node max/min widths, min heights; Edge max widths
* Accumulate sizes correctly for unconstrained multipoint labels
* handle font.multi when groupOptions.font is not declared
* propagate label fonts on changes, not just creation
* Allow top-level constraint numbers
* accumulate width and empty lines appropriately

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

see #909