Automatic merge from submit-queue

Adding a proposal for server-side cascading deletion

@lavalamp @bgrant0607 
cc @kubernetes/sig-api-machinery @derekwaynecarr 

ref https://github.com/kubernetes/kubernetes/issues/12143 https://github.com/kubernetes/kubernetes/issues/19054 https://github.com/kubernetes/kubernetes/pull/17305 (initializer proposal)