Clean up Safe headset volume code [2/2]

Credits: CM

Change-Id: I0a7a30c38ed3da4af9d1c4796cad350970c992a0

Conflicts:
	res/values/strings.xml
	res/xml/sound_settings_rom.xml
	src/com/android/settings/slim/SoundSettings.java
Option to use volume keys to control media volume anytime (1/2)

Some users don't adjust ringtone volume often (e.g. only use toggle to
switch between silent and non-silent) mode. Having an option to
use the volume keys to control media volume anytime allows media
volume to be controllled/muted before entering a game or other apps
with sound in an undesirable location.

mnazim: Adapted for Slim

Change-Id: I6dbd25d1a14bcf5b1bf0b0468b96f4b4f8efdb14

Conflicts:
	res/values/strings.xml
	res/xml/sound_settings_rom.xml
	src/com/android/settings/slim/SoundSettings.java