Settings: Make Safe headset volume handling user configurable (2 of 2)

Patch set 1  : Initial commit
Patch set 2  : Code cleanup and dedupe

Change-Id: I9d46ba5b8ca5a8b18dcb4856c348c86bc3e70899

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

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