Publish "actual_TCP_speed" data field in hardware interface

[rcorralesf]

Hardware_interface doesn't appear to include functionality to read/publish the "actual_TCP_speed" field from rtde. This data is useful when using the robot as both an actuator and a sensor during precise operations.
I would be happy to PR a quick implementation but I am not familiar enough with the driver to suggest a ROS message type. Maybe create a quick 6 float vector message and store it somewhere in ur_robot_driver/include/ur_robot_driver/ros? RobotStateRTMsg.msg from ur_msgs already includes a tcp_speed field but with so many more fields in it I think it would be overkill to reuse it unless everything is implemented.

[fmauch]

We are currently implementing this inside #35. Does that fit your needs?

[rcorralesf]

Yes, that pretty much targets my needs. Is it currently in a usable state?
Beyond that, thank you for your efforts. I totally agree that a proper interface for rtde will be very useful for ROS integrations. Let me know if I can be of any help and do not hesitate to ask for user feedback if you need it.

[fmauch]

The state it is currently inside #35 should be working, but it is not developed on top of the latest master. We expect to refactor this as proposed inside the PR within 2019, but I can't promise anything.

Feel free to comment on the discussion inside #35 and test the features as soon as we push updates. I'll mark this issue to be closed by #35.