- revamp of Settings
- migrated away from SharedPreferences
- all app settings properties are migrated, synchronization settings are reset
- old Preferences can temporarily be exported/imported
- Settings are done in MainActivity, removed PreferenceActivity
- revamp of the players
- both audio and video are now handled in AVPlayer screen (the original AudioPlayer)
- VideoPlayerActivity is removed
- some screens' background color is corrected
- skipped some older DB migration steps, some of which might cause crash
- some code refactoring and reorganization