robot state helper node

[nbbrooks]

FZI will provide input on milestone.

Joint position/velocity/acceleration will already be published on the joint_states topic, so we may not need this

[destogl]

Since ros2_controll it is not needed as a separate component anymore. The values/states have to included into HW interface and then will be published by JointStateBroadcaster.

[urrsk]

@nbbrooks and @destogl Can you provide some more information regarding this suggestion for future-work?
Please include motivation and how you intended it can be used.