1.7.7

1. Add settings to enable/disable thumbstick input
2. Show the exit confirmation dialog when back is pressed
3. Add support for migrating add-on data to Android/media directory
4. Update data and fix bugs
   celestiamobile/Celestia@be1efa4
   celestiamobile/CelestiaLocalization@33ee082
   CelestiaProject/CelestiaContent@9f85700