Oh, FFS NotePerformer

I had to make a change to the app. It turns out that if NotePerformer is installed before Sibelius, then it creates the Sounds directory (which soundsets are put in) by itself. The problem is, it creates the directory so that no other programs can access that directory.

Anyway, so, I've put code in to make the directory writeable so I can put the sound sets in. I'm in the process of updating the other sound sets, but this one was the most important to change.