This class introduces some of the common logic across preference
screens, handling nested PreferenceScreens, as well as the back button
and action bar title setting.
- rename some methods to better indicate their functions.
- make the notification filter to be allow or deny list,
solves #2256 and #336
- make app word filter to behave based on allow/deny settings.
- make Pebble notifications to honor the allow/deny settings.
- add generic "debug function" to Debug activity.
- add Message privacy mode settings, solves #2279
