Sort out Gateway APIs to return accurate information

Current Get Gateways API returns a mix of information that isn't correct. It seems there isn't an understanding that a gateway != gateway cluster, and API returns only the primary gateway within a cluster. Name returned is of the primary gateway and not the cluster name. We should be able to retrieve full information about the cluster, and information about each gateway assigned to it. As other ideas have suggested, we should also be able to use an API to test availability of any individual gateway.