LCS migration : replace warning by a QMessageBox.

src/Gui/ViewProviderCoordinateSystem.h

@@ -83,7 +83,11 @@ protected:
     void updateData(const App::Property*) override;
     bool onDelete(const std::vector<std::string> &) override;
 
+    void finishRestoring() override;
+
 private:
+    void showMigrationDialog();
+
     SoGroup *pcGroupChildren;
 
     std::map<Gui::ViewProvider*, bool> tempVisMap;