Current situation:
- Leveldown needs to be manually opened, and you have to wait for that to succeed.
- Deferred-Leveldown is a temporary leveldown tgat queues operations until it's given the real leveldown
- Levelup initially hosts a deferred-leveldown, opens the real leveldown, then tells deferred-leveldown about it and replaces that with the real leveldown
- If you close the db via levelup, leveldown is closed and deferred-leveldown is put in place again.
What needs to change:
- Levelup should be able to be accept closed, opening, open and closing leveldowns