v4.13.0: OpenTracks

Changes:
- Markers can be created via Public API
  This allows to create Markers at any location and after recording.
  Drawback: Markers are not shown in diagrams anymore.
  NOTE: OSMDashboard supports this API after version: v4.1.0

Bugfix:
- Default activity setting should have been a dropdown
- Back arrow not working in settings
- Label for off trail hiking now shows "off trail hiking"

Developer:
- Use Position instead of Android's Location
