Performance: cache site info for req.params.domain
Performance: cache site info for req.params.domain

Cache the siteinfo used by mediawiki-title in order to prevent
unnecessarily repetitive API calls.

Change-Id: Iacded8e3a60469ca2882b246fcec45b857d38972

wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps,wikimedia/mediawiki-services-mobileapps