Framework: Add the ability to enable/disable use of Profiles

This will remove the Profiles item from the Power menu when the user has
selected to disable the use of System Profiles.

TODO: Better handling of returning a default profile when requested

Change-Id: I3c29b1bbd8f72c5432a1906a6b412d9412279c9f

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