display: Make advanced settings a category

This was a separate screen but it's too empty for that, let's make
it a category like in CM11 for now. If it ever becomes a separate
screen it needs its own fragment so that navigation is possible
via actionbar.

Change-Id: I4b1f3e78a013412d5e39847683ca622dc76b9fa1
Settings: Add proximity wake option

Ports and combines:

http://review.cyanogenmod.org/#/c/66658/
Settings : Add preference for proximity wake

http://review.cyanogenmod.org/#/c/69347/
Proximity Wake-Up : adjust strings

http://review.cyanogenmod.org/#/c/69803/
Settings : Make proximity opt-in

Change-Id: Iea0853eccf764438c7aaac76afd13c364fcea0ec