CGUIMediaWindow: add UpdateFilterPath() method extracted from Update()
fix CGUIMediaWindow::OnPrepareFileItems overrides
CGUIMediaWindow: extract sort information from "xsp" path option
CGUIViewState: extend AddPlaylistOrder() to handle smartplaylist-specific sorting information
CGUIViewStateVideo: add support for smartplaylist-specific sort information
CGUIViewStateMusic: add support for smartplaylist-specific sort information
CGUIViewState: rename AddPlaylistOrder() to AddAndSetSortMethod()