GSOC / Add of new message for OF1.3

Add : 
-  PortFeatures
 - PortConfig
 -MultipartReq (and its dependencies)
 
- add switch description reply (for multipart reply)
If my understanding of the OpenFlow specifications is correct, then an OpenFlow-managed switch will only decrement the TTL of an IP packet if there is an explicit action in a flow to do so. Such actions do not exist in 1.0; they were first introduced in 1.1 and are still present in 1.3. However, `SDN_Types` does not expose those actions. The only way that a packet with an invalid TTL will be received by a switch is if the packet enters the network from the edge or from the controller as a packet out message with an already invalid TTL. In practice, using the abstraction layer with OpenFlow 1.3, packets ins with an `InvalidTTL` reason will be exceedingly rare, if possible at all.

For now, this should not be included in the abstraction layer. Once the OpenFlow 1.3 code in this pull request has been used and battle-hardened, then we can have a discussion about how to incorporate these features into the abstraction. Currently, exposing this one capability of 1.3 in the abstraction is premature and unnecessary.