First pass: Basic editing support for template params

* The spec for template info/content was updated yesterday to use
  a data-mw attribute on the root-element of the template content
  instead of a RDFa meta-tag.

  http://www.mediawiki.org/wiki/Parsoid/MediaWiki_DOM_spec#Template_content

* Verified with a few different test cases.

* Added support for serializing the template transclusion source
  from the data-mw info which should let us reflect any changes made
  by VE (or other clients). Escaping of problematic wikitext in arg
  values is yet to be implemented.

* When in non-rt-testing mode, at least 5 additional wt2wt tests because
  of whitespace diffs introduced by serializing tpl calls via data-mw
  instead of original source.

* To reduce dirty diffs during RT testing, the serializer builds tpl
  transclusion wikitext only when not in RT-testing mode.

* Extensions are not yet wrapped. TO BE DONE.

Change-Id: I661cd00f68c86bff9a608376b6a45015f14de1d3
Merge "First pass: Basic editing support for template params"