Swedish translation update

Updates of the Swedish translation, including minor fixes to the existing strings, but primarily adding translations to the newly added available functionality.

Thanks for picking up this project and restoring the actions! I like the UI, and have been using it for 5+ years by now. I looked into the change in the Gmail request protocols when CheckGmail broke down earlier this year, but I saw little to no progress after hours of debugging and gave it up. I am happy to once again be able to administer mail directly in the tray.

Fun fact: I was the author of the previous Swedish translation update that I noticed that you had already merged from Sourceforge :-) .