Belatedly realised that the design would be clearer without these two
separate concepts being conflated into a single widget.
As a result of this change, any other widget or template that generates
transclude widgets has needed adjustment.
This makes it possible to generate UL or OL lists as well as the
current divs and spans.
This feature is clearly necessary but I'm not very happy with it. It
feels as though the syntax should be modifying a UL tag to specify the
extra information required to generate the list, rather than turning
the list widget to indirectly specify it's elements.
