add grammar for AI aircraft crew member
rename "human crew member" to "human_aircraft_crew_member"
add AIAircraftCrewMemberWasKilled event (close #13)
add AIAircraftCrewMemberWasWounded event (close #20)
add AIAircraftCrewMemberWasHeavilyWounded event (close #21)
add AIAircraftCrewMemberHasBailedOut event (close #15)
add AIAircraftCrewMemberHasTouchedDown event (close #26)
add AIAircraftCrewMemberWasKilledInParachuteByAIAircraft event (close #18)
add AIAircraftCrewMemberParachuteWasDestroyedByAIAircraft event (close #16)
tidy up grammar