this allows the flight code to choose whether FMU failure gives
immediate manual pilot control, or waits for the mode switch to go
past the override threshold

this allows testing of FMU failure behaviour in px4io by monitoring
the reported PWM output when the vehicle code stops sending
updates. Otherwise testing needs to be done with "px4io status" which
is very tedious.

With this change a GCS can monitor the PWM outputs from the failsafe
mixer using normal mavlink messages

this allows for full setup of RC override without needing param_get()
to PX4 specific parameters

Adjust navigator priority

Fix navigator load

Squeeze flash size below 1MB