Improve support for OF 1.3 flow mods

Reviewer: @jnealtowns

We're going to accept OF 1.3 flow mods and stats requests even if the configured version is 1.0. With the related changes to loci and Forwarding (in IVS) I'm able to install OF 1.3 flow mods, send packets through them, and get flow stats for them.

There's more work to do to support multiple versions of flow-mods in the flowtable, or handle stats requests returning flow mods from another version. Not clear that that's a requirement yet.