In this commit, we add the actor system (along with the receiptionist)
and the router.
An actor can be registered with the system, which allows other callers
to locate it to send message to it via the receptionist. Custom routers
can be created for when there're actors that rely on the same service
key and also req+resp type. This can be used to implement something
similar to a worker pool.
Olaoluwa Osuntokun
9ebd8d240d