SystemUI: Pimp-up Media Tile (1/1)

Allow double-click to start a sleep timer
	for the currently playing media.

PS:
- clearer button descriptions on different states
- if timer is in progress restore and show the time the
  user had set up and notify that he is in timer progress

Change-Id: I7848523e7bc3d9577361ff55f010a9909d46e665