Enable the selection of preferred streaming file type for the Magnatune service. this was mainly prompted by the addition of a new ogg stream by Magnatune, but while I was at it, I also added support for the low bitrate mp3 stream for people on a slow connection.

The gui for this is on the magnatune service settings screen. Ogg is now set as the default as in general mp3 is evil! :-)

NOTE: this requires that the magnatune database is updated or it _WILL_ crash

Also a small general fixes