(bug 43498) (bug 43574) Two wikilink types and {{int:}}.

(bug 43498) (bug 43574) Two wikilink types and {{int:}}.

* Bug 43498 - Implement two wikilink types, with tests. Also add test
for external link, which was already implemented in the
main code.

* Bug 43574 - Support {{int:}} message includes in jqueryMsg, with tests.
* Add tests for when the old mw.msg should be called, vs. getMessageFunction.
Change-Id: I7a748eb99259103f491ff5a5aa0bf223fc0b76c4