fixed a bug in the tree display of categories: previous to this fix, a category (with no items assigned) was not displayed, even when its subcategory contained an item. Therefore it was not possible to navigate to the item in the subcategory
upgrade to version 0.27. alignment with xotcl-core 0.38 (use cr_item.name instead of cr_revisions.title), change page_title to title (potential incompatibility) to rely more strictly to the CR data model (most files are effected).