Refactor and clarify where each "job" is started

[strugee]

Right now there are several logical "jobs" that I can think of that the pump system performs:

• HTTP request/response
• OAuth nonce/session cleanup in the database
• Distribution

These are all intermingled with each other in very messy ways. It would be nice to clean these up and separate them from each other, so it's obvious where each is initialized (ideally right next to each other in bin/pump).

In the long run this will help us move towards looking more like a 12-factor app. I'm not sure what that should look like at the moment, but this is definitely a prerequisite.