Add preference for enabling root access (3/3)

 * Root over ADB is now disabled by default on non-eng builds
 * Requires support in su binary and adbd
 * Root access can be configured to use ADB only, apps only, or all

Change-Id: I132a35a31c676511db954ff19120fa6d3c795b23

Conflicts:
	res/values/arrays.xml