mwext-VisualEditor-doc: Update publish and test to match new logistics

* We no longer need a MediaWiki install for the maintenance script.
  bin/generateDocs.sh now uses the HTML files generated by Grunt
  and committed to Git (not a MediaWiki maintenance script).

* The documentation needs lib/ instead of modules/ as modules/ve has
  been moved to lib/ve.

* See also I10eaa5424d172932b in mediawiki/extensions/VisualEditor.git

Change-Id: Ib7ce9c6808f31a47c3ba08697cf405a78eda871d