RemoteControlClient can report current position, speed

Extend RemoteControlClient class to support reporting the
 current playback position, and the playback speed.
Define listener for an application to receive new playback
 position to seek to (use of listener to be implemented).
Update IRemoteControlDisplay implementations to new interface.

bug 8120740

Change-Id: I2654daeca1ac49713d325df8226dceb85943c020