Add a UI (both status as well as interaction with MotoROS2)

[ted-miller]

Now that MotoROS2 is more akin to a real ROS 2 node, we might consider adding a GUI to it.

A UI could be used to both show status of uMotoROS (ie: executing a goal, of length N, expected time to completion, etc) as well as allow users to interact with it (cancel a goal forcibly, toggle some settings, etc).

It would also perhaps be a way to clearly communicate to users holding the TP that "this robot is being controlled externally, using MotoROS2" -- something which is invisible at the moment.

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A GUI for the standard pendant would need to be done by Yaskawa personnel. But anyone with a Smart Pendant could implement an extension. Extensions are created using either Java or C#. (If using C#, please post here first. There are some updates which have not been merged upstream yet.)

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Another potential option would be a simple I/F panel. It's not as pretty or customizable, but it can convey valuable information.