Adds inverse dynamics feed forward terms to joint_trajectory_action.

Current version has debug plotting with matplotlib for parameterization mismatches.
added a mutex to prevent threads from messing up joint trajectory interpolation curves by modifying the current timestamps and indices in the supplied trajectory
wip - added bezier joint trajectories for better trajectory interpolation, but the last segment of the trajectory is being commanded flat for pos vel and accel - this needs to be fixed
fixed clamping of pos vel accel in last bezier segment
force start and end accelerations to zero
Fixed JTAS to accepts multiple command levels.

- Added modular way to detect when velocities and accelerations are
  present
- Plans velocity and acceleration paths *only* if they are present in
  the command
- Fixed Linear algebra 'solve' issue in Bezier when dividing by a scalar
  rather than a vector
- Upped the Joint Trajectory Configuration file's error tolerance to
  0.25
Cleaned Feed Forward plots and comments
Added bezier lib license, removed double server
Cleaned Bezier interface, docs, & pep8 compliant.
Solved FF Joint Command cross-commanding.

The feed forward commands being published from the Joint Trajectory
Action Server were being sent to the wrong joints. This was due to
neglecting to reorder the joint angles, before publishing feed forward.
joint_s0 <--> joint_e0 and joint_s1 <--> joint_e1
This crossover prevented the full potential of the feed forward
trajectories from being visible.

Along the way in debugging, I made improvements to increase
debugging verbosity, and the velocity error limits.
Merge pull request #47 from RethinkRobotics/jtas_inverse_dynamics_feedforward

(Rebase) Inverse Dynamics Feed Forward