Support for multiple xarms

[dmklee]

It would be cool to support sending commands to multiple xArms at once. I think the only change required would be to provide an argument or dialog box to select among possible hid devices found. I am not sure if collision detection, as it is currently formulated, would be possible with two robots; they would have to both exist within a single simulator and the motions would have to be aligned in time

[dmklee]

Reopening this, i think it is a valuable addition that should not take too long. We will need support for multiple arms in the simulator as well.
The major challenge is how to handle monitoring motion. Currently, the monitoring happens in one thread, meaning you would have to move robots at different times.