Make character picker for QWERTY keyboards use HOLO theme

Also, removed the cancel button. Instead, touching outside will close
the dialog.

Change-Id: I20c1d22b131a92e2e2022d054b4141a2b61c7dd8
Improve auto-brightness handling

- Add a setting to control the auto-brightness algorithm responsitivity
- Make the algorithm react much faster when the ambient brightness
  increases quickly, e.g. when receiving a call in bright sunlight.

Change-Id: Ic608901c476609dde69cae982228c09567140a83