Docs questions

[AHBruns]

So, I've been using Commanded for a couple weeks, and theres a few things I really wish the docs had in them. I figured I'd leave them here. If I have time, and a good enough grasp of some of these concepts, I'd be happy to PR docs. As of now, I'm not actually sure I know the answer to these questions:

• Process manager life cycle. It's not at all clear in what order the different callback execute. For example, does after_command/2 execute after apply/2 or before? The life-cycle is important info.
• Process manager persistence. Unlike aggregates where its clear how they are persisted (they have an event stream), aggregates are a mystery. How are they persisted? Where? How are failures handled. E.g. if handle/2 has run but apply/2 has not, will the aggregate re-process the event when it restarts? When does dispatching actually happen?
• Middleware execution. Is after_failure assured to run if the dispatching process dies during the dispatch? What about if the aggregate instance dies during dispatching? What about if the commanded app dies?