Enable virtual undercloud to baremetal overcloud deployments

TripleO and TripleO CI are already creating undercloud and overcloud images [1].

This blueprint is focused on enabling virtual underclouds to deploy to baremetal overcloud systems. There are a couple refinements that could be made to better enable the ecosystem to support such deployments.

Success I think is a few things:

* TripleO is able to specify the contents of an undercloud image that can be used for bare metal deployments
* The image creation process is documented
* Documentation is created on how to use a virtual undercloud to deploy to baremetal overcloud nodes.

Related but possibly not critical for this spec:

* Create a standard for creating undercloud images.
* Test the images as part of the upstream CI.

[1] http://66.187.229.139/builds/current-tripleo/