Settings: 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: I266f0adc1aaf2b28a7735d5b9cc965e699f06a6c

Conflicts:

	res/values/cm_arrays.xml
	res/values/cm_strings.xml
	src/com/android/settings/DevelopmentSettings.java

Conflicts:
	res/values/cm_arrays.xml

Conflicts:
	res/values/cm_arrays.xml
	src/com/android/settings/DevelopmentSettings.java