Settings: disable lockscreen settings appropriately

Give visual feedback on which features are unavailable
with the new lockscreen style.

Change-Id: I05b905e9a6e48d884943156b2dedc93ceee57bc4
Signed-off-by: Roman Birg <roman@cyngn.com>
settings: Make mobile settings a first-class citizen

 * Nobody likes carriers, but let's not bury these settings behind
   10 layers of indirection. Many users (like me) who travel often
   will need to access these options frequently.
 * The top level switch disables mobile data.

Change-Id: I1bd4d1116a2c73832230d66c94df2c3c0aacf698