Settings: Update to follow new volume design.

- "Sound & Notification"  (not Notifications)
- Remove ringer-mode pref.
- Add zen-mode pref to renamed "Interruptions" screen.
- Implement two separate "Sound" & "Notification" sections.
- Remove "Showing notifications" screen, migrate settings.
- Remove custom category styling now that we have a platform style.
- Implement new "days" sleep mode and corresponding dialog pref.
- Corresponding changes to indexable resources.

Associated frameworks/base change:
  I35afe38646f04d2ba0dbac11c2c6356120a33694

Bug:15831713
Change-Id: I6ed56791784968adfbd684f490dbbebed285a2dd