minor updates to mussa setup widget

I was trying to get mussa to build against qt 4.3.0 which and this component
had some display issues (which I wasn't able to resolve on OS X)
these updates remove the trailing blank space that was needed for qt 4.2.2
on windows (at least I think it was that version) and wrapped most
of the display strings in the tr() so we could localize mussa if we
wanted to.