Currently `kubectl get all` outputs
`images.caching.internal.knative.dev`, but it is one of internal CRDs
and not necessary to examine the output in general.
This patch removes `all` from categories to stop printing
images.caching.internal.knative.dev in kubectl get all.
* Add a label knative.dev/crd-install to CRDs to allow installing CRDs in a separate pass.
* YAML cares about types, and `true` is a Boolean, not a String.
* Add the initial caching type definitions.
This is largely carried over from https://github.com/knative/serving/pull/1972
* Incorporate feedback from @evankanderson
* Add the CRD for the type definition.