ofctl_rest: support Port Modification Message

this patch makes ofctl_rest enable use of Port Modification Message.

usage)

  URI:    /stats/portmod/{dpid}
  method: POST

the message body is as follows:

  port_no    (default:0)
  config     (default:0)
  hw_addr    (default:automatic-setting)
  mask       (default:0xFFFFFFFF)
  advertise  (default:0)

e.g.)

  curl -X POST -d '{"port_no": 1,
                    "config": 0}' http://localhost:8080/stats/portmod/1

Signed-off-by: TAKAHASHI Minoru <takahashi.minoru7@gmail.com>
ofctl_rest: enable getting Description of a port

this patch makes ofctl_rest enable getting Description of a port.

usage)

  URI:    /stats/portdesc/<dpid>
  method: GET

e.g. )

  curl http://localhost:8080/stats/portdesc/1

    {"1": [{"hw_addr": "c6:d8:19:4a:e1:4f", "curr": 0, "supported": 0,
            "max_speed": 0, "advertised": 0, "peer": 0,
            "port_no": 4294967294, "curr_speed": 0, "name": "s1",
            "state": 1, "config": 1},
           {"hw_addr": "8e:96:a1:14:d8:a1", "curr": 2112, "supported": 0,
            "max_speed": 0, "advertised": 0, "peer": 0,
            "port_no": 1, "curr_speed": 10000000, "name": "s1-eth1",
            "state": 0, "config": 0}]}

Signed-off-by: TAKAHASHI Minoru <takahashi.minoru7@gmail.com>