QmlDesigner: Variant types for Binding Editor

- Variant and alias types proper support
 - Extended instantiation options for Editor
Task: QDS-2264

Change-Id: I95ff24fb81ce64b4effc64803304ff2b150a7ff6
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/bindingeditor/bindingeditordialog.cpp

@@ -225,7 +225,7 @@ void BindingEditorDialog::setupComboBoxes()
     m_comboBoxItem->clear();
     m_comboBoxProperty->clear();
 
-    for (auto bind : m_bindings)
+    for (const auto &bind : m_bindings)
         m_comboBoxItem->addItem(bind.item);
 }