Create spatial actuator issue62

This branch adds BodyActuator to OpenSim and edits Actuator Class for its vector output. 
Thanks for the suggestions Ajay. I can apply them, just since I don't have Simbody 3.5 installed yet, I wont be able to test them locally before passing to Travis. It would be great if any of you could do the corrections for now. Otherwise, I'll install it tomorrow and come back to your suggestions.