Remove unused alpha layers
Used induced qbuar for propwash effects
J3Cub: Elevator control strength increased.
J3Cub: Particle spray and smoke should be non-emisive.
J3Cub: Rudder and elevator FDM tweak per aircraft model.
J3Cub: ITGA Update through July 16, 2017.
J3Cub: Refactor, optimize payload logic.
Provide a simple addon skeleton
Add spoken ATC addon
Adopt ATC chatter to new addon api (--addon=/foo/bar switch)
