Remove TODO around clearBuffer API.

We decided at the Sept 2013 F2F to leave them as is.
Remove TODO around Query API

As decided at Sept 2013 F2F
WebGL2RenderingContext typo.
Add getIndexedParameter into IDL
Remove WebGLRenderingContext API from WebGL 2

At the same time, update the WebGL 1.0 latest spec with
the [NoInterface] WebGLRenderingContextBase interface.
Remove texImage3D. Add HTML element entry points for texSubImage3D
Update getIndexedParameter signature.
Merge pull request #383 from grorg/post-sept2013-f2f-edits

Post sept2013 f2f edits