Give link widget support for configuration variables

One can now use `\define tw-wikilinks() no` to disable wikilinks, and
`tw-wikilink-template` to configure the link template.
Fix output type for view format `htmlwikified`
Fix typo in macro variable substitution
Let the new rendering methods accept a parent widget
Fix typo
Fix static tiddler template
Add a new version of rendertiddlers command

So that we can test static html generation
Test building static css and individual tiddlers
Content updates