Added geographic login restrictions.

Made a user preference that allows users to only allow
logins to their account from a specific country. The
GeoIP database, which is CC-BY-SA licensed, and the
PHP library for GeoIP, which is LGPL licensed, are included
to determine the user's location.

Change-Id: I1e8441661bb5cade897e08fb504a654edb2d7e6a
Merge "Added geographic login restrictions."