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