ENH: Detect WebGL support.

A note is display suggesting how to get it if it is not found.

Also, use itk namespace for javascipt functions.

Change-Id: I2fef0306d034144b59acef56607fff9ae686c466
COMP: Add missing breathe.css to generated HTML.

Change-Id: I5e0dae29feaffa9bd815319b2bc6f6a9be54c3a4
Merge "ENH: Detect WebGL support."
Merge "COMP: Add missing breathe.css to generated HTML."