Redesign settings on tablets

1. Move ContactsPreferenceActivity to ContactsCommon since it is called
   in DisplayOptionsPreferenceFragment, which is built as part of Dialer.
2. Remove preference_headers.xml since we are going to get rid of headers.
3. Kitkat backporting.

Here's how it looks:
https://docs.google.com/a/google.com/presentation/d/1A5n2o8epBCrizZvbOyelvjoHz-s5-IRlJd-KqWAMBao/edit?usp=sharing

Bug: 25629359
Bug: 26469731
Change-Id: I2dc8dec8a6e3725c3180f0e0a56ed68fe28cca50