ADD option $checkbox_vertical_columns to render_search_field().

* Depending on how your site looks, not all columns might fit using the
  crude heuristic that was in place.
* Note, this still allows less columns to be used, depending on the
  number of items.



git-svn-id: http://svn.resourcespace.org/svn/resourcespace@5839 c08608d7-6e46-0410-86ca-f2a6f1370df5