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/metrics/setup.go

@@ -89,7 +89,7 @@ func prometheusParse(c *caddy.Controller) (*Metrics, error) {
 					return met, e
 				}
 			default:
-				return met, c.Errf("unknown item: %s", c.Val())
+				return met, c.Errf("unknown property: %s", c.Val())
 			}
 
 		}