Settings: Enable AppOps

Enables back the AppOps activity and add a warning dialog on system
core app. Adds a "Apps permission" section under Personal.

Change-Id: I1d53d9430bd00003040b997e6ba939923847035f
Signed-off-by: Scott <scott@ubuntu>

Conflicts:
	res/values/custom_strings.xml

Conflicts:
	res/values/bs_strings.xml