Enabling navigator, does not do anything useful yet
Fix the direction of the override switch for the new state machine
easystar startup script: load mixer from sd-card if available
Hotfix: Improved file test
tone_alarm: add GPS warning tone
Introduce geofence boundary detection framework

- Add function to detect whether craft is inside or outside of geofence
- Don't use C++ style comments in C files
- Add fence topic
- Correct a few unit description comments
- Update navigator to maintain craft status with respect to geofence