wx GUI: Introduce a DataViewModel
wx GUI: Expand DataViewModel
wx GUI: Improve code
Core: Add get_item_parent to API
Core: Add get_root_items to API
Core: Add get_item_children to API
Core: Improve code
Core: Improve code
wx GUI: Start replacing TreeCtrl with DataViewCtrl
wx GUI: Adapting to DataViewCtrl
wx GUI: Adapt comments to DataViewCtrl
wx GUI: Reorganize tree initialization
wx GUI: Improve code
Core: Add get_all_items to API
wx GUI: DataViewCtrl adaptations
wx GUI: Improve code
wx GUI: Adapting to DataViewCtrl
wx Links: Adapt to recent changes in wx GUI
wx GUI: update_tree_image -> update_tree_item in API
Core: Add functions to API