Follow-up from "Support Kubernetes PVCs"

The following discussion from !606 (merged) should be addressed:

• @zj started a discussion: (+1 comment)

  We should add support for ConfigMapVolumeSource.Items

  @tmaczukin Given I'm leaving for my two weeks of vacation soon, I'd like to cut scope now and ship what we have. I just pushed the docs. Would you be ok with that? If so, I'll create an issue from this comment