Merging dev branch into main (#32)

* Serialize and deserialize fixed-length arrays like ROS does (#21)
* Commands Unity can send to manage the ROS endpoint
* Message Generation Browser and Scripted Importers
* Adding ROS# headers, acknowledgements, and special thanks.
* Added ROSGeometry library
* Process more than one message per frame
* Close the socket OnApplicationQuit
* The AssetImporters namespace moved in 2020.2

Co-authored-by: mpinol <mpinol@users.noreply.github.com>
Co-authored-by: Peter Smith <thisisntanemailaccount@gmail.com>