Fix loading of extensions + start migration towards HTML5-style link fragments
Created by: lahwaacz
I added a git submodule for the Nuke extension and used the wfLoadExtension
function for extension loading as recommended by MediaWiki.
The migration to HTML5-style fragment links (see Manual:$wgFragmentMode) is two-step, first the html5
mode is enabled as secondary and then it is switched to the primary mode. I will do this in another PR about a week after this one is merged.