Gui: Use auto and range-based for (#7481)

* On lines where the variable type is obvious from inspection, avoid repeating the type using auto. 
* When possible use a ranged for loop instead of begin() and end() iterators

src/Gui/Flag.cpp

@@ -134,7 +134,7 @@ void Flag::mouseMoveEvent(QMouseEvent *e)
     if (e->buttons() & Qt::LeftButton) {
         move(e->globalPos() - dragPosition);
         e->accept();
-        View3DInventorViewer* viewer = dynamic_cast<View3DInventorViewer*>(parentWidget());
+        auto viewer = dynamic_cast<View3DInventorViewer*>(parentWidget());
         if (viewer)
             viewer->getSoRenderManager()->scheduleRedraw();
     }