Internal improvements (1)

- Reordered AndroidManifest.xml
- Replaced hardcoded strings by strings in Strings.xml
- Reordered imports
- Renamed MainActivity to SettingsActivity
- Renamed Settings to SettingsFragment
- General cleaning and refactoring
SettingsFragment improvements

- Created SummaryListPreference to handle the Listpreference summaries
automatically
- Use SummaryListPreference instead of Listpreference
- Fixed FC by missing EXTRA_NEW_DIR_NAME for the dir chooser intent
- Fixed not building by ignoring missing translations