Joint Trajectory Action Server Improvements

* Splines! Adds linear, cubic and quintic spline segment generation. Adds 'position' control mode switching.
 Allows for direct position commands to JCBs. Accurate trajectory tracking.
* Adds clean control mode switching on exit.
* Adds new dynamic reconfig param file for position jtas controller.
* Adds parameter overrides from trajectory action requests. Execution trajectory tracking, goal, goal time tolerances take priority when provided in action request.
* Adds cuff interaction monitored control mode switching. Exits back to standard joint position control mode when cuff pressed.