v3.12.0: OpenTracks

Changes:
- Bluetooth sensor addresses
- Intervals: show elevation gain
- Export: default export directory
- Export: automatic export after finishing a track
- Manual import/export: new user interface
- Manual export: option to overwrite on manual export

Faster:
- Track lists loading
- Deleting multiple tracks

Bugfix:
- Fixed intent filters for import
- KMZ could not be parsed
- Export: fix crash on Android 11

Developer:
- Use ViewBindings
- Database enforces foreign key a