This also removes the 'navigator fence <lon> <lat>' command to simplify
code (I don't think there's still use for that anymore). However the
file loading is still supported.
If goefence.txt does not exist, navigator will not clear the geofence
anymore on startup.
It makes more sense to set the optimization flags on a platform basis
instead of individually for each module. This allows for different
optimization options for SITL, NuttX, Snapdragon, etc.
Beat Küng