Settings: per-app cellular data, vpn and wifi restrictions

*) Add options to disable all cellular, vpn and wifi data
   in app data usage settings.

*) Disable the existing background data and unrestricted
   data usage options when all cellular data access is
   disabled.

*) The vpn data option can be selected independently from state of
   all Wi-Fi and mobile data access enable/disable.

*) Prevent DataSaverBackend from overwriting uid policies

This is a replacement for the appops menu based cell/wifi data
restriction settings in cm-13.0:
Author: Danesh M <daneshm90@gmail.com>
Date:   Mon Mar 7 15:17:59 2016 -0800
    Settings : Add per app internet/data control
    CYAN-3976
    CRACKLING-834
    Change-Id: I13192df837c057b5cadde8f31532e12daaf3c1b0

Change-Id: Ic087c27a5ed0bdb84bb8f297c425c6bcbffec848
(cherry picked from commit d4a2eea6)