Update jquery.i18n to f6102aa4feddf3623c9fba3a3d31592c58204b58

From https://github.com/wikimedia/jquery.i18n/tree/f6102aa4feddf3623c9fba3a3d31592c58204b58

Also rename jquery.i18n.messages.js to jquery.i18n.messagestore.js ,
somehow these files are named differently between the version in ULS
and the version in github and I didn't pick up that change when
switching between them.

Change-Id: Icd78c1374969f1ea539938237d405a8aeecd1dd7
Merge "Update jquery.i18n to f6102aa4feddf3623c9fba3a3d31592c58204b58"