Treat "abolished" subscriptions as if they have been deleted by Azure

[Iain-S]

When we "abolish" a subscription, we set it's net approval and allocation to £0 as we presume that this subscription has been deleted on Azure and cannot spend any more. We also filter the frontend table based on abolished status. However, we do not prevent admins from making new allocations/approvals and I'm not sure that any further logic changes (e.g. do we still return abolished subscriptions to the controller function, etc).