Add test that recreates bug #293

ReceiveActor never receives any messages if Base.OnPreStart isn't called from PreStart override
ReceiveActor should be initialized from ActorCell instead of doing it itself.

Fixes bug #293.
If the user did not call base.PreStart() or base.PreRestart(), Init() was never called
This introduces a new interface InitializableActor, wich has an Init method that is
called by ActorCell instead.
Merge pull request #294 from HCanber/receiveactor-293

ReceiveActor should be initialized from ActorCell