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.
It displays internal configuration information for debugging and
learning about TiddlyWiki. Also introduces a way of interleaving
documentation tiddlers (complete for tiddler fields, more module type
docs to come)
Get rid of the separate renderContext stack and instead have a parent
pointer on renderer nodes. This lets us walk back up the render tree to
resolve context references
