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.
Not yet complete - we can't add or remove fields, and we need to
trigger type-specific editors for certain field types. And the layout
is a bit rubbish at the moment
Templates are the low-level bits and pieces that allow TW5 to generate
HTML and CSS renderings of tiddlers. The UI folder contains the
user-visible UI of TW5
