Implement disk usage reporting for the administrator
The current report is no longer updated by the backend job that used to do it, so we need something to replace this. The columns in the current report include:
User Collections Read Size Collections Persisted Storage Measured At Total (unweighted) Shared (weighted) Total (unweighted) Shared (weighted)
With the addition expired/trashed collections, we probably want to report stats on that as well to show how much space is available to be reclaimed/garbage collected and perhaps what will be expiring "soon."