Bug 50587: Parse template parameters to DOM or other non-wikitext types
where possible

Output template args as encoded HTML in data-mw:parts.template.params.

New blacklisted result: References: 6. <references /> from a transclusion
(html2html) due to parserTests not knowing how to normalize the about
attribute inside an HTML template parameter.

Change-Id: Idba17c0b2276ee1117d86abcc6aae40989c3ba38