[KFileWidget] Use KMessageWidget for error reporting
Instead of a KMessageBox. It's a lot nicer :)
(Didn't dare touching KDirOperator, though)
Seems to reliably go away when navigating to a different folder (not entirely sure under which circumstances urlEntered is and isn’t emitted)
I wonder if KDirOperator should emit canceled when jobError occurs?
The error message boxes ("can only select one file", "file could not be found", etc) when accepting the dialog are kept.