mw/kubernetes: remove federation and cidr (#916)

* mw/kubernetes: remove federation and cidr

Remove both as we have a corefile syntax change that handles cidr and
remove federation because that is going to be its own middleware.

* backwards incompat changes

This PR:
* removes cidr from kubernetes (core Corefile feature now)
* removes federation from kubernets (comes back as new middleware)
* [remove autopath - which was already gone, so that already was
  backwards incompat]
* adds `fallthrough` to the *etcd* middleware and makes you enable it.
* Fail on unknown properties
* documentation
* Disable TestHealthCheck as it uses realtime and fails

middleware/etcd/handler.go

@@ -46,7 +46,10 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 		if opt.Debug != "" {
 			r.Question[0].Name = opt.Debug
 		}
-		return middleware.NextOrFailure(e.Name(), e.Next, ctx, w, r)
+		if e.Fallthrough {
+			return middleware.NextOrFailure(e.Name(), e.Next, ctx, w, r)
+		}
+		return dns.RcodeServerFailure, nil
 	}
 
 	var (