Classified failsafe_abortable as profile variable
Tiny comment adjustment
Added failsafe flightmode and rc control box

For support and in preparation of rewriting the failsafe system.
Must be possible to trigger failsafe with a rc switch or when rc control
signal is lost. Also configurable if a started failsafe may be aborted
or not when the rc control comes back online.
End of day commit (untested)

Failsafe rewritten (untested).
The failsafe flightmode is activated by rc control signal loss and/or
may be activated by a rc switch.