remove comment from Host __unicode__() for consistency (we do not have the comment in Domain __unicode__() either)
add help for adding a host, cosmetic changes to adding a domain help
clarify hostname in querystring must by same as username used for http basic auth
support notfqdn api result code

we do not really need it as far as the service is concerned (we would give some other valid failure result code),
but it might help to user to more quickly find the mistake in his client configuration.