Deleting Buckets and Snapshots

To simplify cleanup tasks in KBC storage we've added support for deleting non-empty buckets.  You no longer have to delete any tables before deleting your bucket, so this should save some time when cleaning up your workspace.

We've also added support for deleting table snapshots, which should be helpful when working with tables and snapshots.

Both functions are available through the KBC Storage API, documented here: "drop bucket"  and "delete snapshot"