[Unstable] ReliableDeliverySupervisor, RemoteWriter, RemoteReader, Stash support

Getting closer on issue #1

In this pull request:

* Implemented all of the endpoint actors: `ReliableDeliverySupervisor`, `RemoteWriter`, `RemoteReader`
* Added ACK support to `AkkaPduCodec` - also tested to make sure that there isn't any data loss between SeqNo wire format (ulong) and internal protocol format (long)
* Implemented basic Stash support, along with some user-usable actor types i.e. `UntypedActorWithUnboundedStash` and `UntypedActorWithBoundedStash`

Working on EndpointManager, then the Remoting classes, then finally TCP transport + RemoteDaemon / RemoteActorRefProvider integration