Add new app ops for various interesting audio service things.

Media buttons: note when an application tries to take ownership
of the media buttons.
Audio focus: note when an application tries to take audio focus.
Volume levels: note changes to the volume level of the various
streams.

Maybe we should also have some ops for muting streams, soloing
streams, etc?

Change-Id: I79a5d477b0bad4ff61486cdb73ffb1196a674964