Add a "target_pose_lookahead_time" parameter

[AndyZe]

This work was started in #886. Closes #696.

The new parameter helps account for latency in the control loop. This can compensate for various issues or delays in the control loop that are hard to quantify, including:

• joint_states publication rate
• ROS message transmission. There are usually 2 message hops when Servo is used
• network latency
• a little bit of processing time
• whatever happens in the ros_control interface
• low-level controller ramp up/ramp down time

[AndyZe]

@livanov93

[mergify[bot]]

This pull request is in conflict. Could you fix it @AndyZe?

[henningkayser]

@AndyZe what is the status of this?

[AndyZe]

It could still be useful. It's stuck somewhere between "potentially useful" and "useful enough that I want to merge it now".

[mergify[bot]]

This pull request is in conflict. Could you fix it @AndyZe?

[tylerjw]

@AndyZe if you rebase this and it passes CI, I'll approve it. What do you think?

[AndyZe]

I'll just close this since it's not clear if it would be useful. Let's remember this in the future in case Servo is laggy, though