Simplify creation of arrival aircraft

[n8rzz]

current workflow could be simplified. the current process is:

ArrivalBase.preSpawn()

AircraftController.aircraft_new(options)
- airlineModel = window.airlineController.airline_get(options.airline);

AirlineModel.generateAircraft(options);

AirlineModel._generateAircraft(options);
- options.callsign = window.aircraftController.aircraft_callsign_new(options.airline);
- options.icao = this.chooseAircraft(options.fleet);
- aircraftModel = window.aircraftController.aircraft_model_get(options.icao.toLowerCase());

AircraftModel.generateAircraft(options);

AircraftModel._generateAircraft(options);
- options.model = this;
- const aircraft = new AircraftInstanceModel(options);
- prop.aircraft.list.push(aircraft);

There is a lot of back and forth here that could be simplified. This should all be accomplished from within the AircraftController.aircraft_new() method. Making all the various calls from within that single class instead of passing an options object around to 4 different class methods.

[n8rzz]

#243

[erikquinn]

This issue was moved to openscope/openscope#59