Create spatial actuator issue62

This branch adds BodyActuator to OpenSim and edits Actuator Class for its vector output. 
I've done some of the above-mentioned changes locally, but need to test them locally first. 
I will be out of office till next Tuesday and I'll come back to this PR afterwards. Sorry for the hold guys. I hope no one needs this PR merged till then! 
@aseth1 @sherm1 @chrisdembia