Volume panel changes.

Combined volume panel only in tablets. On phones show active volume.
Added dummy assets for ring+notification icon.

Deprecated the NOTIFICATION_USES_RING_VOLUME. Now they are always
tied together. Audio manager changes still required to ensure that.

Initialize all feedback sounds to true.

Change-Id: I3ad7890c9be9334eedb5f3b709a4b6995fe24638