And, while we are it, clean up DNSZone so that it has separate notions
of TaskName, DNSName and HostedZoneID. We conflated the three
previously, which we don't want to do at the task layer. We don't want
to conflate the TaskName and the DNSName so that we can create a private
& public hosted zone with the same DNSName. We don't want to "smuggle"
the hosted zone ID in the DNSName because it doesn't belong in the task
layer.
Fix#1374
* Zones are now subnets
* Utility subnet is no longer part of Zone
* Bastion InstanceGroup type added instead
* Etcd clusters defined in terms of InstanceGroups, not zones
* AdminAccess split into SSHAccess & APIAccess
* Dropped unused Multizone flag