Turns out the generator sets this bit when it reaches the
maintenance-required state.
Mask it out from the error bits so the user can still fly.
Add some periodically-run code to complain about maintenance-required,
separate from the prearm checks.
AP_Generator_Richenpower: only update servo channel while disarmed
AP_Generator_Richenpower: move warning for servo output channel to prearm checks
AP_Generator: state is simply off if RPM is zero
AP_Generator: send runtime and seconds-until-maintenance in GENERATOR_STATUS
AP_Generator_RichenPower: correct runtime seconds/minutes position in packets
AP_Generator_RichenPower: correct and expand use of mode packet entry
AP_Generator_RichenPower: fail prearm check if generator not seen
AP_Generator_RichenPower: make prearm check for needing maintenance warn-only
AP_Generator_RichenPower: rename runstate to pilot_desired_runstate
AP_Generator_RichenPower: tweak decoding of time-to-maintenance
AP_Generator: add hysteresis for warmup/cooldown in IDLE
AP_Generator: stop generator in case of vehicle crash
AP_Generator: generator must go through idle from run to stop
AP_Generator: emit statustext when generator configured but not present
AP_Generator: do not log if LOG_BITMASK is zero
AP_Generator: do not warn user if generator configured but not present
They won't be able to start the generator if we can't see it.
Don't update the runstate if no readings seen.
AP_Generator: do not send generator status if no readings seen
Peter Barker
Andy Piper
Gone4Dirt
Andrew Tridgell