Fixed object/part splitting

If object has additional settings and we split it, add this settings for each of the new objects(parts)

src/slic3r/GUI/wxExtensions.hpp

@@ -443,6 +443,7 @@ public:
 	wxDataViewItem DeleteLastInstance(const wxDataViewItem &parent_item, size_t num);
 	void DeleteAll();
     void DeleteChildren(wxDataViewItem& parent);
+    void DeleteVolumeChildren(wxDataViewItem& parent);
 	wxDataViewItem GetItemById(int obj_idx);
 	wxDataViewItem GetItemByVolumeId(int obj_idx, int volume_idx);
 	wxDataViewItem GetItemByInstanceId(int obj_idx, int inst_idx);