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.

This is not about reinventing how Docker handles images or an attempt to make Kubernetes also a Docker registry; instead, we're hoping to facilitate concepts such as:

- a virtual unified view of image repositories potentially spanning multiple registries
- reacting to image changes to perform a variety of actions, such as downstream builds or new deployments
- allowing users to override default image metadata consistently when an image repository changes
- dealing with Docker image metadata in a time series, for the purposes of making images easily consumable by other components of a deployment system

I had envisioned that a pod would be required to specify how much disk space it needs and the kubelet will enforce that.  So, no denial of service allowed. 

I could certainly see the Images object including size information about each image, and a tool that helps set pod disk limits correctly from image sizes.  So, I agree with your use case, just not the last bullet.