Automatic merge from submit-queue
Add support to quota pvc storage requests
Adds support to quota cumulative `PersistentVolumeClaim` storage requests in a namespace.
Per our chat today @markturansky @abhgupta - this is not done (lacks unit testing), but is functional.
This lets quota enforcement for `PersistentVolumeClaim` to occur at creation time. Supporting bind time enforcement would require substantial more work. It's possible this is sufficient for many, so I am opening it up for feedback.
In the future, I suspect we may want to treat local disk in a special manner, but that would have to be a different resource altogether (i.e. `requests.disk`) or something.
Example quota:
```
apiVersion: v1
kind: ResourceQuota
metadata:
name: quota
spec:
hard:
persistentvolumeclaims: "10"
requests.storage: "40Gi"
```
/cc @kubernetes/rh-cluster-infra @deads2k
6ae6450a39