Settings: Remove sound settings.

- Move the remaining conditional preferences into
  the combined Sound & Notifications screen.
- Refactor the "Other sounds" sub-settings screen to
  provide a home for the new preferences.
- Migrate docking sounds, conditional on config.
- Migrate docking media, conditional on config.
- Migrate emergency tones, conditional on CDMA.
- Move all boilerplate preference <-> setting plumbing into
  a separate helper.
- Since some preferences in Other sounds are now conditional,
  create a special indexer for searching.
- Remove SoundSettings (and xml), create aliases in the manifest
  to avoid breaking shortcuts.

Bug:15279526
Change-Id: I5ae3ecda2f899b1948f7908bd217a799326c2c56