Self-check order events

[ptrwtts]

Occasionally when an order changes in status, no event is created. We've been unable to determine why. This causes anyone relying on our events to go out of sync, which is bad.

Beyond finding the bug, the thinking is to run a process that looks over our events, and makes sure that the result you get from following them is the same as the current price / status in our database. If not, it either self-heals or triggers an alarm.