title: QML: How to get the QModelIndex in a delegate inside a TreeView
body: <p>I have a delegate in a qml <code>TreeView</code>. I would like to get its <code>QModelIndex</code>. Vía</p>
  
  <pre><code> model.index
  </code></pre>
  
  <p>I only get the number of the row, where the delegate is. However, I need to pass a <code>QModelIndex</code> to the c++ side (to make a <code>QPersistentModelIndex</code> and store it for later use).</p>