Make chunk IDs strings and fix programGlobal

programGlobal is set to chunkClass.prototype, not chunkClass. Chunk IDs
are made to always be strings, rather than a mix of strings and numbers
as they previously were.
Merge pull request #319 from NVIDIA/fix-programGlobal

Make chunk IDs strings and fix programGlobal
Fix feature index example link
Support for transparent canvas
Fix examples index
Update morphing examples

Morph between three targets instead of two in one of the examples so that
it tests the case where the morph keys change. Correct comments to say
that only morphing positions and normals is supported, others are not
supported by the shader. Also make the morphing range consistent with the
comments.
Merge pull request #320 from NVIDIA/update-morphing-example

Update morphing examples