Reference: Support for {{cite...}} template adaptation

Updates the references in translation section by following
https://www.mediawiki.org/wiki/Parsoid/MediaWiki_DOM_spec#Ref_and_References

This has effect only when the language pair has a tempalate mapping
defined.

References are experimental feature, enable this using
$wgContentTranslationExperimentalFeatures = true;

Change-Id: I9e11b747a355c7f7e5c88fc45931cbe5f4192972