Changed the missile model to also include thrusters for rotational purposes and gave them the same exhaust shader.
Each shader is a unique instance and displayed thrusts can be set with set_X_rotational_thrust(), set_Y_rotational_thrust() and set_main_engine_thrust() in the missile root respectively.
Also added a second missile in the space scene just for debugging purposes.
Created a missile model with 4 exhausts in Blender and imported it with collision shapes (not tested yet if they work).
Created an exhaust shader with a simple particle trail. The shader that creates the exhaust flame can be adapted to the missile burn power.
