Add initial resources.md for discussion

The first draft of a Kubernetes resource model.
Any kind of ordered id range, perhaps application-specific (not tied to hardware), related to custom hardware, or even site-specific (available user-ids?). These are not urgent requirements, and we can move on with a scalar-only implementation for now. We can add ranges/sets later if/when important use cases arise. I just wanted to raise some awareness now. Curious to hear @johnwilkes thoughts upon his return.