[cob_twist_controller] Limiters

[fmessmer]

• We need acceleration limiters: see https://github.com/ipa320/cob_control/issues/53#issuecomment-142904976
• We need a consistent way for configuring limits (pos(-tolerances), vel_limits, acc_limits)!
  They could be retrieved from URDF, joint_limits.yaml and reconfigure and then always choose the "tightest" limits

[fmessmer]

acceleration limiters are implemented in fmessmer@73cf606
to be tested with hardware...

[fmessmer]

Problem was mainly related to ros-industrial/ros_canopen#141
Disabling ros_control's joint_limit_interfaces helped....still acceleration_limiting should be handled in cob_twist_controller!
For now, only dummy implementations have been added....

[fmessmer]

Acceleration Limiters have conceptually been added.
However, implementation not leading to a satisfying behavior.
Also, the main problem was caused by faulty behavior when using velocity_controllers together with ros_control/joint_limit_interface.
Therefore, joint_limits.yaml has been removed and behavior is satisfying for now....
Still #56 should be investigated further!