I9100G: Add backlight trigger selection

Kernel commit: http://review.cyanogenmod.org/#/c/43597/

Patch Set 2: Removed enable backlight function, made it so that
backlight timeout option would be disabled if trigger area is selected
as none.

Patch Set 3: Update code to reflect new kernel sys interface.

Patch Set 4: Fix derp

Patch Set 5: Use One Class.

Patch Set 6: Some cleanup.

Change-Id: I85563be938282c430e097b87b553dcacfeb14905
Merge branch 'cm-10.1' into martincz