i18n: remove BOM character

Change-Id: Icadcc7d4e421a99e5b3f5b57d8ecc57209dc4dff
Migrate to JSON i18n

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

Change-Id: I0651aee45de35291f1d48f725a7dffd564c10f17