Special:Protect site cleanup

This set of commits rewrites the SpecialProtectSite extension to bring it in line with the Nirvana framework and new MediaWiki standards. The outline:
* Removed the ProtectsiteForm class in favor of SpecialProtectSiteController extending WikiaSpecialPage controller
* Templatized the UI thanks to this
* Now using $app->registerSpecialPage when setting the extension up
* Global references omitted in favor of $this/$app->wg
* Replaced wfMsg() calls with wfMessage()->text()
* Marked the methods for the profiler.

I'm not entirely sure if I comprehended the exact workings of how Nirvana handles templates, due to out-of-date documentation.