This removes a lot of the ArduPlane specific cruft left over from the
initial Rover import from ArduPlane, plus fixes a bunch of serious
bugs. For example, the rover was unable to use either compass or gps
for heading - it used just gyros!
There is still a lot of cruft left, but this at least gives a bit
better basis for future work
Added option (hold roll to full right + SW7 ON/OFF) to init_home during the wp_list reset
Add ROV_SONAR_TRIG (default = 200 cm) - tested by Franco
Restart_nav() added and heading bug correction, tested OK in the field
RTL then stop update - Tested OK in the field
Added SONAR detection for obstacle avoidance
Signed-off-by: Jean-Louis Naudin <jlnaudin@gmail.com>