AliasGenerator returns full URL instead of relative

AliasGenerator::getVariation always returns in the .uri part full URLs (including protocol and host) instead of relative URLs. This is not only in contradiction to the specs in https://doc.ez.no/display/EZP/The+Image+FieldType .

This is due to the fact that IORepositoryResolver::resolve inserts the base URL in https://github.com/ezsystems/ezpublish-kernel/blob/master/eZ/Bundle/EzPublishCoreBundle/Imagine/IORepositoryResolver.php#L96

This issue also introduces heavy problems when the webserver is behind a https: proxy. The generated link includes http as protocol, however it should be https, which the webserver nerver sees.