Framework: Make Safe headset volume user configurable (1 of 2)

Patch set 1  : Initial commit
Patch set 2  : Alternative approach using content observer to
               listen for settings changes and react dynamically
Patch set 3  : Rebase

Change-Id: I0bd57334ca1307786eaed6578b216323e442f00e

Conflicts:
	core/java/android/provider/Settings.java
	media/java/android/media/AudioService.java