MediaProvider: MediaScanner behavior on boot (2/3)
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: Iad0b72f8b653b3d567b27de3ccf5c6cfb07e40ed
Merge remote-tracking branch 'temasek/cm-10.2' into cm-10.2