Move volume adjust sound option to more native place (2/2).

Our new UX concept includes saving more settings headers possible.
Move this into Volumes settings fragment. Also update description string.

PS2: Update description string.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

Change-Id: I6243e27582dd0099da4b3b12b30a4e5cb8247dac
Merge "Move volume adjust sound option to more native place (2/2)." into kitkat