Merging dev branch into main (#22)

* Renaming and reorganizing package to better catkinify/pep8ify
* Commands Unity can send to manage the ROS endpoint
* Unregister the old handler when a new one is registered (#21)
* Rewrite server core loop
* Handle socket timeout
* Remove the pointless threads list
* Start the server on its own thread

Co-authored-by: Devin Miller <devin.miller@unity3d.com>