title: Qt5 QML QVariantMap Binding with change notifications
body: <p>I have QVariantMap (not QObject, because property names are not predefined). And I inject QVariantMap into QML root context to use property values for binding.</p>
  
  <p>The problem is that when I change QVariantMap or even when I change QVariantMap and call setContextProperty for updated object, or when I update (with fromValue) object returned by contextProperty nothing happens. So this looks like one time binding.</p>
  
  <p>So, what is the right way in inject Map or Map into QML context in observable way, so that changing item in the map will be reflected in QML?</p>