add a neutron port-scheduler component

Jan-24-2016(armax): talked to Kevin. This looks superseded by the latest direction adopted by routed networks spec and may no longer be relevant.

Jan-18-2016(armax): no major code nor documentation as of today. Changes of getting in Mitaka are getting slim. This was always a long shot anyway.

Dec-07-2015(armax): related on routed-networks. Needs more specification

Dec-08-2015(kevinbenton): The primary use case for this is the routed networks spec. I initially planned for this to help with the get-me-a-network spec, but that design has gone in a different direction than I had envisioned so it doesn't seem to be necessary for that. So until the routed
networks spec is ironed out, this will just be on hold.

Jan-14-2016(sean-k-mooney): i have been doing some work of late on a proposal to expose neutron related host capabilities that may be related to this work. the proposal suggest the creation of a new neutron api for use in neutron port binding, ml2 mechanism driver selection and network aware placement of vms by the nova scheduler . i hope to send a mail to the mailing list in the next few weeks to solicit feed back form key stakeholders in nova and neutron and a draft spec with usecases and a datamodel that should be to also address some of the network segment reachability requirements of the routed networks spec though that is not the focus of the work i have been doing.