Add support for Brightspace group format CSV

Added method to autodetect Brightspace group format in the CSV service, and added logic for remapping from the Brightspace format to the GitBull format. I've attempted to make it relatively updateable.

I don't have a proper gitbull setup, so I was not able to look at the students page nor test the functionality. I hope you will be able to do so.

Closes #43 (closed) Closes !14 (closed)