Migrate to JSON i18n

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

Change-Id: If6b61df5042e575587b8806887b2d822447c2287
Replace deprecated/removed $wgExtensionAliasesFiles

Change-Id: If72abbf7db411fa4cbefe0f82220614381896316