Port forward over websockets

- split out port forwarding into its own package

Allow multiple port forwarding ports
- Make it easy to determine which port is tied to which channel
- odd channels are for data
- even channels are for errors

- allow comma separated ports to specify multiple ports

Add  portfowardtester 1.2 to whitelist

pkg/kubelet/server/streaming/server_test.go

@@ -240,7 +240,7 @@ func TestServePortForward(t *testing.T) {
 
 	exec, err := remotecommand.NewExecutor(&restclient.Config{}, "POST", reqURL)
 	require.NoError(t, err)
-	streamConn, _, err := exec.Dial(kubeletportforward.PortForwardProtocolV1Name)
+	streamConn, _, err := exec.Dial(kubeletportforward.ProtocolV1Name)
 	require.NoError(t, err)
 	defer streamConn.Close()