Enable MobileFrontend on wikidata.org

This is needed to see better what's left to be done to display Wikidata
on mobile devices, and to satisfy a dependency for WikiGrok which will
soon be deployed there in repo mode. Because we're not enabling mobile
domain or mobile redirection, this is essentially a shadow deployment.

Change-Id: Iaea3924c5a75124932ed78bdb80cd5517cf51bca
Merge "Enable MobileFrontend on wikidata.org"