Return: Expandable Volume Overlay

The option to customize the expandable volume overlay has been
orphaned since the dawn of time(or SlimKat in this case).
Bring back the setting for the same. The frameworks change is
already in the source.

This also fixed the OnPreferenceChanged keys

PS 2-4: Cleanup and MultiUser

Change-Id: I59d3ac8bfc8ea7ee08e4e2ed006aa432e4a929c4
Merge "Return: Expandable Volume Overlay" into kk4.4