Remove the StreamID named type #484
Description
This is a minor breaking change that I think we should probably make: it doesn't make sense that ServerSession.ID is a string, but our StreamID type is a distinguished type. Stylistically, either is OK, but we should be consistent, and certainly StreamID is significantly less important conceptually than a session ID: why does it get a named type?
I don't think anyone is implementing a custom EventStore, so this should be a non-event, but once we tag v1.0.0 we can't do it. I think we should do it tomorrow.