redo the stackorder based on where the item is.

With the keyboard navigation patch there is the issue that sometimes, due to sorting by SortFilterModel, the stack order of the items doesn't correspond to the visual order of the items. This is a problem wrt the recently introduced keyboard navigation, as the tab order of items in qml is completely tied to the stack order, resulting in an erratic tab navigation order (usually happens with device notifier or bluetooth applets for instance)