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/multi_test.go

@@ -16,6 +16,7 @@ import (
 func TestMultiLookup(t *testing.T) {
 	etc := newEtcdMiddleware()
 	etc.Zones = []string{"skydns.test.", "miek.nl."}
+	etc.Fallthrough = true
 	etc.Next = test.ErrorHandler()
 
 	for _, serv := range servicesMulti {