Visibility of catalog items in twinio adjusted.

Previously, catalog items were automatically hidden in the tool overview of twinio as soon as there were no more individual tools. From now on, catalog items will remain, even if all associated individual tools have been deleted.

Users can still view, edit, and specifically remove the catalog items if necessary. New individual tools can be added using the + symbol at the beginning of the respective row. This maintains the structure and allows the visibility of the catalog items to be controlled individually.