Migrate to JSON i18n

Procedure per https://www.mediawiki.org/wiki/Manual:GenerateJsonI18n.php
with shim.

Change-Id: I77a75fe00b3e44e0622852a949fc6ee625f815ba
Replace deprecated/removed $wgExtensionAliasesFiles

Change-Id: I627955ffa11bb1473af9598d00d312f7bf6487c2