Add back backlight curve adjustment.
Some post-merge cleanup for automatic brightness adjustment

- Remove some unused strings
- Use (device-dependant) minimum brightness level (as calculated by
  DisplayPowerController) as '0%' instead of the actual value 0.

Change-Id: I79123d2421c9ab35fa0f1808d82d785463e8fbaa
Settings: fix incorrect value in autobrightness adjustment

If the user drag the progress bar below the min value, the incorrect
setting will be saved since seekBar.setProgress code path does not
return to the "getItem(pos).backlight = ..." line.

Change-Id: I4796e22ba9c44315be92de4040f6cd8451bdf153
Overhaul auto-brightness level UI.
Correctly restore brightness customize dialog hierachy.
Make menu item title and help text consistent.
fixed some derps
Added some missing strings and arrays for auto brightness