Updating sv.po

[Mattias Engdegård]

The Swedish translation has not been updated for many years and is in  
rough shape. I'd like to try giving it a thorough overhaul, some  
lubrication and a new coat of paint.

This is going to take a while. Finding no listed maintainer to  
contact, I'm assuming the translation is orphaned at the moment.  
Please tell me how to proceed; absent specific instructions, I'm just  
going to roll up my sleeves and start working, and solicit reviews  
when done.