Framework Track Control : Switch from broadcast to audio service

Ordered broadcast is unreliable.
Switch to using the Audio Service's dispatchMediaKeyWithWakeLockToAudioService
as it sends the event to the correct receiver.

Patchset 2 - Switch power widgets over as well
Patchset 3 - Rename handler 'what' message to be more consistent
Patchset 4 - Fix renaming mishap

Change-Id: I022720a551b94637f7b16258dfb6a22234bcb736