CM71: Add option to wake phone with volume keys

- Added on public user demand
- Originates from EVO, where power button is hard to press
  and no trackball available for waking device
- Option located under TrackballWake option
- No check for available volume buttons done, since i asume, each
  device got volume buttons. correct me if i am wrong.

Note: removed loads of trailing spaces with auto save actions.
blame the original creator (;

Change-Id: Ia45a68cc0d034b816939e2563f5c3596279b252b