Add global action for screen recording. [2/2]

Change-Id: I618691b1607b86d831d3ae66747c65343fac8a9f
MediaScanner behavior on boot (3/3)

Lets you enable/disable/ask (with a notification) media scanning on boot.
Can speed up boot and reduce initial boot lag from MediaScanner

Change-Id: Ib476117cf1c2b5e8de11a828287c300f30a596b5