integration-docroot-jslint never worked (fetch mw/core)

The job template '{name}-jshint' is hardcoded for MediaWiki core so
there is no point in applying it to integration/docroot.git

Change-Id: I6cd09cccb9c1a150d5a3a1f27a08c765c01cb304
{name}-jslint job template is now generic

The jslint job template was hardcoded to fetch MediaWiki core which
prevented the template from being reused on other projects.

That slightly change mediawiki-core-jslint job which is now deleting its
workspace and recloning the repository (still without submodules). That
is fast enough by my tests.

I have assigned the jobs to hasSlaveScripts since it needs jshint.

Change-Id: I7048bd5712b43b96ffd51cf4e0d5e38bde59ec3a