Storing the active printer technology onto the Undo / Redo stack,

remembering the last selected Printer profile for the SLA and FDM
technologies separately, and activating them on Undo / Redo.

When switching the technologies, user is asked whether to discard
the modified profiles or not.

src/slic3r/GUI/GUI_ObjectList.hpp

@@ -317,7 +317,6 @@ public:
     void change_part_type();
 
     void last_volume_is_deleted(const int obj_idx);
-    bool has_multi_part_objects();
     void update_settings_items();
     void update_and_show_object_settings_item();
     void update_settings_item_and_selection(wxDataViewItem item, wxDataViewItemArray& selections);