Modify OpenFlow commands related to ports to be more expressive.

Modify OpenFlow commands related to ports to be more expressive.

This new OpenFlow message format provides a cleaner interface and greater
detail and control over ports.  It is now possible to see what features
the switch's port is currently configured as having, what it's advertising,
and what it's capable of handling.  It is also possible to return the
features advertised by the port's peer.