Fragmentize the dialpad UI

Moved most of DialpadActivity into the new class DialpadFragment.
The old DialpadActivity is now just a simple container for the fragment.

TESTED (on crespo):
  - Dialing an outgoing call
  - Options menu (only visible once you've typed at least one digit)
  - "Dialpad chooser" scenario (the special UI when you bring up the
    dialpad while a call is already active).  Note that text colors in
    the dialpad chooser items are wrong; that'll be fixed by some
    upcoming theme cleanup.

Change-Id: I8827727bb2bc86936c4ef23e1a307ac04141c1ea
8 files changed