moved over aircraft listings

Demo:
-removed aircraft_in_airspace
+removed initialisation in start()
-removed recently_departed_airspace
+removed initialisation in start()
-removed getAircraftList()
-removed getAvailableEntryPoints()

GameWindow:
-added aircraftInAirspace, recentlyDepartedAircraft
-added getAvailableEntryPoints()
-added getAircraftList()