v3.18.1: OpenTracks

Changes:
- Deleting tracks is handled by a service
- Uninstall deletes all data (i.e., hasFragileData=false)

Bugfixes:
- Race condition: crash while recording and switching OpenTracks into background
- Search in track list was not working
- Cycling speed sensor: distance computation was wrong (only affected statistics)

Developer:
- ControllerFragment replaces TrackController