* Detect CoreOS
* Move key manifests to code, to tolerate read-only mounts
* Misc refactorings so more code can be shared
* Change lots of ints to int32s in the models
* Run nodeup as a oneshot systemd service, rather than relying on
cloud-init behaviour which varies across distros
So the flow is that we recommend (or strongly recommend) a new kops
version when one is required for a new version, and then the new kops
version will recommend (or strongly recommend) a new k8s version.
We don't have a notion of multiple recommended k8s versions per kops
version - that is what channels are for.
Users are always free to disregard updates, even "required" ones by
setting a flag.