Port away from deprecated KMessageBox::sorry()

See frameworks/kwidgetsaddons!142 (merged) (merged) for the motivation. Note how "No matches" in MainWindow::Window::slotShowListOfFiles() is proposed to be an information instead, as one could argue this is not an error, but a normal result.

Replacement API exist in older KF API, so no version checks needed.

Currently KPhotoAlbum holds the concept of "sorry" still in own API in UIDelegate::sorry & friends. This patch does not touch that, because the mapping of KPhotoAlbum information categories to Qt/KF API categories is something you developers might have own ideas and might need separate discussions.