TListBox displays a list box on a Web page that allows single or multiple selection.
The list box allows multiple selections if {@link setSelectionMode SelectionMode}
is TListSelectionMode::Multiple. It takes single selection only if Single.
The property {@link setRows Rows} specifies how many rows of options are visible
at a time. See {@link TListControl} for inherited properties.
Since v3.0.3, TListBox starts to support optgroup. To specify an option group for
a list item, set a Group attribute with it,
$listitem->Attributes->Group="Group Name";
or in template