LegacyUSB: Squashed commit with updates for 4.2

LegacyUSB: add overlay for UMS lun and use existence of lun to enable legacy USB

LegacyUSB: Add support for legacy USB implementations

Rebased for ICS 4.0.3

Option to hide Adb notification icon (framework) - authorship belongs to Rick C

Change-Id: Id14f70f7e21b689c08cadef69f69da711c7dc566
Add option for switching between UMS and MTP/PTP mode. (1/2)

Change-Id: I8e692d468cb36ccc97ca69b8a2eb11afeb711eae

This adds support for switching between UMS and MTP/PTP.
Framework part (this part) will only enable UMS if the config setting is set.
Standard is to enable UMS if the primary volume supports UMS.

It's only porting this http://review.cyanogenmod.org/#/c/21117/