Menu and Radiobox options which allow "no selection"

[njk42]

It would be nice to have MenuOption and RadioboxOption which allow the Menu and Radiobox components to be configurable with "no selection" behavior, instead of the current behavior which forces exactly one item to be selected. (Note this is different than Checkbox which can have none, some, or all items selected.) A new "no selection" behavior avoids the need to define (and take up screen real estate with) a separate item called "none" or "unselected" or similar. Alternatively, provide a way to hide the rendering of this "none" item.