Added unsupported_validator

dnszone attributes idnsallowquery and idnsallowtransfer have valid but currently unsupported values: 'localhost' and 'localnets'.

New validator was introduced for unsuported values. By using this validator user can see that the value is currently unsupported instead of showing 'invalid value' or passing the value to server and creating error there.

https://fedorahosted.org/freeipa/ticket/2351

ipalib/plugins/internal.py

@@ -574,6 +574,7 @@ class i18n_messages(Command):
                 "min_value": _("Minimum value is ${value}"),
                 "net_address": _("Not a valid network address"),
                 "required": _("Required field"),
+                "unsupported": _("Unsupported value"),
             },
         },
     }