increase qunit coverage of mediawiki.html and mediawiki.util
- mw.html
* Adding test for mw.html.Raw
* Adding more tests for mw.html.element
- mw.util
* Minor coding style update (local variables)
* Updating mw.util.addPortletLink to not create its own "#mw-panel",
this was previously done for ./qunit/index.html (which has been
removed) but when ran on [[Special:JavaScriptTest/qunit]] it collides
with the existing "#mw-panel", so far didn't break anything but that
was purely lucky. This element is redundant so taking it out of the
html sample
* Removing redundant clean up, #qunit-fixture is automatically cleaned
after each test
Change-Id: Iaf9791ca3cdcac1b732c851cdecc8fcd9f96fdd8