Rover: use mission.start_or_resume()

this allows the user to setup whether a mission restarts or resumes
SITL: prevent unused parameter warnings
AP_Rally: fixed indentation

previous indentation confused emacs24
Plane: removed some usused code

setting up flight modes by CLI is not used any more
AP_HAL: prevent some FastDelegate warnings
SITL: disable missing initializer warnings

not specifying all initializers is normal