ok, second try: make use of KDirSortFilterProxyModel. 'Show in Groups' still works...

ok, second try: make use of KDirSortFilterProxyModel. 'Show in Groups' still works, haven't tested nepomuk part though.

NOTE to dolphin devs: please, consider using 'left.column()' instead of 'sortRole()' in lessThan methods, and 'sorting()' instead of 'sortRole()' in other places.
Didn't make switch by myself because it needs nepomk testing (shouldn't be too hard though).

svn path=/trunk/KDE/kdebase/apps/; revision=692517