Add resolutionScaleFactor to CesiumWidget and Viewer.
Force a resize when scale-factor changes.
Fixes after review.

1. No need to have forceResize property in Viewer.
2. Fix typo in CesiumWidget.
Use property setter.
First cut at resolutionScale uniform.

Still need doc updates and cleanup.
Ongoing resolution scale work.
Merge remote-tracking branch 'origin/master' into resolutionScaleFactor

Conflicts:
	Source/Widgets/CesiumWidget/CesiumWidget.js
Simplify resolutionScale by removing it from the scene and computing it automatically in UniformState.update.
Fix billboards
Update CHANGES.
Revert no longer needed changes.
Add specs.
Remove Buffer doc
Add options to ClearCommand and remove doc
Remove public CubeMap and createShaderSource doc
Add options to DrawCommand and removed doc
Remove more Renderer doc
Remove ShaderCache doc.  Minor lifetime cleanup.
Remove Texture doc
Remove UniformDatatype