test: add mininet-test suite

This patch adds a test framework using mininet. The following tests
can be performed.

- Set the flow for the OVS-switch from Ryu-app, we test the actual
  packet is to be handled properly in accordance with the flow; The
  packet that generated by "mz" or replayed by "tcpreplay" is routed
  through the ovs-switch, are processed according to the flow, then
  compare test conditions and the results captured by "tshark".

- Create a packet with ryu using the packet-lib, we test the packet
  and response are correct; to compare test conditions and the results
  captured by "tshark".

  $ ./run_mnet-test.sh [OPTION] [TEST DIR or FILE]...
  $ ./run_mnet-test.sh l2 l3/icmp packet_lib/arp/ARP_gratuitous.mn
  $ ./run_mnet-test.sh --help

Requirements package:
 - mininet: git://github.com/mininet/mininet.git
 - openvswitch: git://openvswitch.org/openvswitch
 - Mausezahn 0.40: http://www.perihel.at/sec/mz/
 - TShark 1.6.2: http://www.wireshark.org/
 - tcpreplay 3.4: http://tcpreplay.synfin.net/

Signed-off-by: HIYAMA Manabu <hiyama.manabu@po.ntts.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>