ListModel provides no way to turn a row number into a QModelIndex

I expect this was overlooked when exposing QModelIndex & other related classes/changes like QItemSelectionModel to QML in Qt 5.5.

The result of this is that it appears (to me) to be impossible to use ItemSelectionModel with a ListModel-type model.

Found via http://stackoverflow.com/questions/41566115/purpose-and-usage-of-itemselectionmodel-in-qml