docs: Overhaul of the RenderScript reference documentation.

cherry-pick from CL: https://android-review.googlesource.com/148241

This CL replaces the Doxygen generated documentation by one that's created
by our internal tool found in framework/rs/api.  The big advantages:

- Can handle overloaded functions.  Doxygen could not and RenderScript has many.
- Can have version information.
- Can match the look of the Java documentation.
- Cleaner look and no leaking of internal paths.

This CL also include changes introduced by the L release which was missing
previously.

Change-Id: Icade41d04d35e45c445ad952bb8ce14389f9f59f