RemoteControlClient receives playback position change requests

RemoteControlClient defines two listener interfaces for playback
  position, one to let the framework query the current playback
  position, the other to request playback to seek to a given
  position.

Updated IRemoteControlDisplay interface to support passing info
  about whether the user of RemoteControlClient can provide a
  playback position, and receive a new one.
Updated implementations of IRemoteControlDisplay to new
  interface.

Bug 8120740

Change-Id: I1a5a969da4d0f8c9ad27f691919dd08f8653982b