Add to/tweak mediawiki and jqueryMsg JS tests, fix comment

Add to/tweak mediawiki and jqueryMsg JS tests, fix comment

* Remove getOuterHtml.
* Use htmlEqual where getOuterHtml was used, among other places.
* The comment reflected a change I considered making, but did not in the end.
* Add a few link tests
* Minor tweaks to other test code for consistency
* Replace wikiGetlink with explicit output

Change-Id: Id6a857c9686901f8db4944fcc081d4b9c4457fa8