Add license information

The code in this repo is missing a license. While the client is using the "GNU GENERAL PUBLIC LICENSE Version 3", server and data uses "GNU AFFERO GENERAL PUBLIC LICENSE Version 3".

@fxedel @mvdan @eighthave Which license do you prefer?

I'll wait until all commented on this and then push a license. I prefer GPL but have to say that I don't know the difference to AGPL.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information