Inverse Dynamics FeedForward

The Inverse Dynamics Feed Forward update to Baxter's Joint Trajectory Action Server (JTAS) is meant to 

- Create smoother interpolated paths between trajectory points that are passed into the server by using Bezier curves. These curves keep the interpolated trajectory continuous in 3 dimensions (position, velocity, acceleration) for each joint
- Allow faster movements when using JTAS by feeding forward the trajectory's velocities and accelerations commands into the motor controller
- Maintain compatibility with trajectories that supply position-only trajectory points
YES! I hadn't seen this before, and my fix was to add a mutex to prevent trajectory interference. I'll remove the double start. but leave the mutex for now (since it wont cause any harm).