3581 IPv6 support

I think this resolves #3581.
- updated geoip api from https://github.com/maxmind/geoip-api-php v1.14
- updated GeoIP/Php.php (and LocationProvider.php)
- added a test

Am I correct to see that only the GeoIp\Php class needs modification? GeoIP\Pecl still doesn't seem to work with IPv6 and GeoIP\ServerBased seems to handle IPv6 already?

Running `console tests:run --file tests/PHPUnit/System/ManyVisitorsOneWebsiteTest.php` fails on some assertions (not mine). For now, I kept those as they are.
here you could reuse the implementation in the [Network component](https://github.com/piwik/component-network) eg. `$ip instanceof \Piwik\Network\IPv6`