v3.24.0: OpenTracks

Changes:
- GPS is optional (also for indoor use): if using a BLE sensors that provide distance are used
- Settings: option to disable BLE filtering of devices
- Charts: altitude starts at minimal value instead of 0m.
- UI supports showing stored timezone information

Bugfix:
- Re-added workaround for crash due to clock traveling back in time (workaround was removed in v3.23.0)
- Removed unecessary workaround for BLE cycling sensor (RTFM)
- GPX importer did not handle missing