Disable global forwarding per-zone
    
    bind-dyndb-ldap allows disabling global forwarder per-zone. This may
    be useful in a scenario when we do not want requests to delegated
    sub-zones (like sub.example.com. in zone example.com.) to be routed
    through global forwarder.
    
    Few lines to help added to explain the feature to users too.
    
    https://fedorahosted.org/freeipa/ticket/3209