Add multiwiki role for wikidata

This is going to be the coolest thing you have ever seen!!!1!

Provisions a new multiwiki instance named 'wikidata' and installs the
full WikiData stack using the WikidataBuildResources repo from WMDE's
github repository. All other multiwiki instances on the VM will be
configured as wikidata clients.

Change-Id: Ifd9c7693204da8a6841f4a2512aae9dde45591c0