(CE-1184) Apply MediaWiki 1.19.23 release

Apply the MediaWiki 1.19.23 release.
(CE-1184) Apply ExpandTemplates security patch from MW 1.19.23
(CE-1184) Apply Scribunto patch for MW 1.19.23
Merge pull request #5822 from Wikia/release-256-CE-1184

(CE-1184) Apply MediaWiki 1.19.23 release