Add support for AVRCP 1.3.

* Add metadata support.
* Add player settings support.
* Add playback support.

A2DP Settings App support.

Bluetooth: A2DP Sink support for Settings App

- add support for A2DP Sink in Settings App. This will enable connection
  initiation and updation on Settings App
- add framework Apis to support A2DP Sink. Any third party Apps can access
  A2DP Sink priority of device and playing state of device
- add support for key to set priority. This manages priority of device for
  A2DP Sink profile

Change-Id: If5f9139f37cdb9d200387877c7801075205c78a0