ListDialogDemo added.  Add layoutOrientation property to ListView.  Add ...

ListDialogDemo added.  Add layoutOrientation property to ListView.  Add graphicsConfiguration method to UIElement.
null should be avoided, something like 
```
    longValue.foreach( lv => {
      prototypeCellValue = lv
      visibleRowCount = -1
    })
```
and make longValue: Option[String]