Introducing Openflow NX Extension infrastructure and NX_RESUBMIT action in ovsdb project

- This infrastruture will make use of the openflowplugin's extension infrastructure to add to the Extensibility tree.
- Few of the NX actions and matches will be introduced here and ideally all the NX actions should reside in a OVS friendly place.
- NX_RESUBMIT and NX_RESUBMIT_TABLE codec are added and the appropriate action type will be used based on the data passed by the application
- Fixed Distribution to make use of this infra.

Change-Id: Ibdc634afe7704c9a4890a952ddb4bff5ef066610
Signed-off-by: Madhu Venugopal <mavenugo@gmail.com>