Add PolylineGlowMaterialProperty

This allows for DynamicScnee materials to make use of the PolylineGlow type.

Note, CZML does not support this material yet.
Merge remote-tracking branch 'origin/master' into polylineGlow

Conflicts:
	CHANGES.md
Clean up returns whitespace
Remove doc links to czm_ GLSL identifiers
Merge master to refdoc-2
Fix reference doc readonly/constant
Merge branch 'master' into refdoc-2
Clean up use of see in reference doc
Rollback cesiumWorkerBootstrapper
Better use of multiple examples in reference doc
Merge master to refdoc-2
Merge remote-tracking branch 'origin/master' into refdoc-3
Better ICRF code example
Reference doc for Appearance options
Document primitive exceptions
Merge master to refdoc-2
Merge branch 'refdoc-2' into refdoc-3
Merge branch 'refdoc-3' into refdoc-4
Merge remote-tracking branch 'origin/master' into polylineGlow

Conflicts:
	CHANGES.md
Cleanup after merge.