- Fix / improve GUI function: make tree view a proper tree view by passing item names as text= of the Treeview nodes, so indentation of the names is present now
- Add vertical and horizontal scrollbar to all tabs
- make tree logic simpler and clearer: remove mirror_trees from DataTree and add it to Catalogue. Catalogue now does operations on all trees separately.
make GUITree actually an subclass of Treeview as well, instead of having Treeview as attibute of GUITree