Release notes for kops 1.15 series

(The kops 1.15 release has not been released yet, this is a document to gather the notes prior to the release).

Significant changes

kops now supports running with objects as CRDs, stored in a kubernetes apiserver.
The apiGroup for kops objects has changed from kops to kops.k8s.io, to support CRDs. You can continue to provide either apiGroup as input (but you should ideally move to kops.k8s.io), but the output will always be of the kops.k8s.io form.
Rolling updates are much faster by default. A lot of the time-padding that was in previous versions has been replaced with reliance on validation. The --cloudonly case is much faster than previously, which we believe to be correct because we expect this is normally for disaster-recovery scenarios, but you may want to specify longer timings via flags if you are relying on time-based delays.

If checking the output as a string (yaml or json), please note that the apiGroup will now be kops.k8s.io, not kops. If performing strict string comparison you will need to update your expected values.