Enable api to select the event store to persist to and replay from

[daviddawson]

When scaling a system, it is unlikely you will remain with a single event infrastructure. Instead, you will likely want to persist some events into a "local" event store, and others into one for inter service comms. (E.g. the difference between aggregate root internal events and external domain events).

This requires being able to specify, by name or tag, the event store to use on emit and replay.