Rename to ItemEntry.

To differentiate from the deprecated ListboxItem class.
Allow modification of window size.
Don't create windows for list and map.

The UI elements for these adapters are handled separately.
Fix incorrect lua.
Use vertical layout widget.

Rather than our own stackable container hack.
Fix issue with clipped windows.

If max size isn't set, the windows are clipped to the size of the app
window. By setting the max size of the windows inside the scrollable
pane to a rather high value (6000 pixels should be enough for
everyone...) we'll avoid this.