Create spatial actuator issue62

This branch adds BodyActuator to OpenSim and edits Actuator Class for its vector output. 
SWIG is reporting a syntax error on:
`<void constructStructuralConnectors() override;>`

Here I tried adding {} at the end.. did not help.

The same syntax seems to be working fine in `<Joint.h>` in master. 
Any idea how to resolve this? @chrisdembia @sherm1