Start of aerodynamics

Created a rough algorithm for aerodynamics. Applies drag and lift. Still
isn't that fun to play with. Needs more work.
Fixed Aerodynamics bug

Aerodynamics was applying drag twice instead of applying lift. Now it
applies lift.
Added flaps

Added flaps to the engines, controlled by the triggers.
Merge pull request #2 from michaelwiktorek/simon

Aerodynamics