Treeviewleafitem class is needed when creating treeviews. It allows you to define the individual
items for each column of a treeview leaf. You have to use as many <item> declarations as
there are columns in your treeview. Since this class is a subclass of Treeviewleaf class,
your <item> declarations have to be embedded inside the <leaf> tag. Leaf items can
have a label and optionally an icon. See Treeview class for an example.
Note that you cannot create instances of this class using moai.CreateObject(). Instead, you have to use Treeview.InsertLeaf to create leaf items at runtime.