due to the recent tagging freeze this commit contains several fixes in one:

* the filterbar now also filters directories (works also in the column-view :-))

* The "Additional Information" menu entry now also works for showing/hiding the columns of the details view. This also implies that the columns for the details view can now be adjusted per directory -> we have now a consistent behavior between the icons view and details view. Still open: the view properties dialog must be fixed

* Don't show a "Nepomuk not available" error message when starting Dolphin and Nepomuk is not available.

* Fix issue that the information panel blocked the application because of parsing the full meta data of a huge file.