title: how to set a custom qfilesystemmodel in qfiledialog
body: <p>I'd like to show a virtual file system alongside the normal file system in a qml file dialog. For that virtual file system i will use a customized class derived from qfilesystemmodel.</p>
  <p>However how can i tell the qml file dialog to use my custom model?</p>
  <p>I have seen in the
  qml/QtQuick/Dialogs/DefaultFileDialog.qml source code, that it has a <code>modelComponent</code> property but I don't know how to modify that property. Can anybody help? Is this even the right way to achieve it or should it be done in another way?</p>