Proposal: Initial images proposal

This is a proposal to add a higher level image component that can keep track of Docker image repositories, images, and image metadata.
It's captured as a point in time, but there's a distinct difference between the metadata that exists in a pod (set this and this) and the metadata that you offer for someone who wants to consume your image (this image has X or Y).  For instance, down the road an image author will want to say "this image works best with > 512mb of RAM".  The metadata in the pod says how much memory is used, but that suggestion / constraint is not something that would be in the pod.