SafeRefresh for file watchers was unnecessary

Remember the cross-thread issue we had with the sound picker?  Turns out the solution was just to set the FileSystemWatcher's 'SynchronizingObject' property to the form handling the events, this guarantees that the event handlers will be called on the same thread as the form.

VS sets this property automatically when you add a FileSystemWatcher in the designer, which is why the exception didn't happen with the project tree.

On a sidenote, I also implemented F2 renaming for files.