Update jquery.i18n from upstream

Upstream: https://github.com/wikimedia/jquery.i18n
Changes:
 * Support fallback loading when folder is passed as source to load
 * Do not overwrite existing messages for a locale while adding messages
   second time
 * Fix the country code case issue
 * Renamed jquery.i18n.messages.js to jquery.i18n.messagestore
 * ULS: Updated Resources.php for renaming of jquery.i18n.messages file

Change-Id: I60a6e3224cb7b8ea813a8ccd7e389071b3d1244c
Merge "Update jquery.i18n from upstream"