App ops: media ops, set up to be callable from native code.

This is to help implementation of bug #8181262 and maybe
bug #8181261

Adds some definition for media ops (though nothing is yet using
them), and re-arranges things a bit so we can implement native
calling in to the app ops service.

Also add some java docs.

Change-Id: I637959745db820e676f23a35a5d2224f51bc6689