Add Swedish translation

This is an early Swedish translation. I have not had any chance to test this translation inside the app to see how it looks since I'm currently on a Linux machine.

Some sentences became a bit long, but all of them went through a few revisions to shorten them down a bit. I hope they fit in the GUI.
How can I preview this when I get back to my Windows machine? Do I just need to place the file at the proper location or do I have to compile the project for it to show up?