Dormant operations

These are the operations necessary to support dormant stores. We still need a way to call IssueCreditWhenDormantOp periodically. Since we haven't figured that out for other operations yet either, we'll defer it for now. Also, this picks an arbitrary amount of the monthly bill to refund (80%). We will probably want to make this configurable in the future. I was thinking about how this could be described in the tier definition.