Add support for Open vSwitch TFM

[gizmoguy]

@blp has added support for setting table names via TFM for openvswitch in this branch:

https://github.com/blp/ovs-reviews/tree/multipart-requests2

Open vSwitch being a software switch has no reason to allow modifications to their pipeline, so we need to add a feature to faucet where we can do a table features message request to load the capabitilities of a given datapath, modify this request to inject table names, then play back a table features message to set table names.

[blp]

For what it's worth, OVS should allow requests to remove features from its pipelines. They will have no effect. If my interpretation of the OpenFlow spec is correct, this is allowed and perhaps desired behavior; maybe it makes implementation on the Faucet side simpler.

[gizmoguy]

Hey @KitL since you were the one that was doing the proof of concept work on this one, did you try that and did it work?

[anarkiwi]

Fixed by #3112