This commit adds a Binding object. The idea is that schedulers can write
these to cause pods to be asssigned to hosts. I'll provide an implementation
along with a rudimentary scheduler plugin.
This continues k8s' tradition of phrasing all APIs as RESTful handlers.
* Made externalize/internalize generic to prevent boilerplate.
* Add fuzz testing.
* All objects pass fuzz tests now.
* This turned up some things we'll need to fix eventually. Left TODOs.
