This commit has some improvements for the code related to the OpenFlow 1.2
The changes are:

    - On match unpack, insert the proper match tlv object. (e.g, if the oxm field is
an inport, insert and inport object).
    - Add a compare method to oxm_tlvs and match_list, because there was not how to test
if the match in messages like flow_stats or flow_removed were correctly sent by the switch.
    - Improvements to the print format of oxm_tlvs.

Also, there is a minor fix for the groups test.
Merge pull request #34 from CPqD/master

Changes to the OpenFlow 1.2 match framework