complete portDesc module
Merge pull request #125 from fugitifduck/master

GSOC / Add of new message for OF1.3

This pull request is the first part of @fugitifduck's GSoC project.
The following changes are included:
Extend set of supported Oxm fields
Extend set of supported actions
Extend set of supported instructions
Add missing marshal, parse and to_string functions
Add PortConfig
Add PortFeatures
Add FlowRequest
Add QueueRequest
Add TableFeatureProp
Add TableFeature
Add TableFeaturesRequest
Extend MultipartReq
Add SwitchDescriptionReply
Add FlowStats
Add AggregateStats
Add TableStats
Add PortStats
Add QueueStats
Add GroupStats
Extend MultipartReply
Extend Error
New QuickCheck unit tests for OF0x04 types
Merge pull request #129 from fugitifduck/portDesc

complete PortDesc module