Separate master and forward DNS zones
    
    Forward zones are stored in idnsforwadzone objectclasses.
    
    design: http://www.freeipa.org/page/V4/Forward_zones
    
    Ticket: https://fedorahosted.org/freeipa/ticket/3210
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>