Added tell supervisor action to make system init work

Fixes #16 (closed) by introducing a new tell supervisor action, that is sent additionally to the ActionJoinAnswer message. If the answering node does not know the supervisor yet, it will postpone the "tell supervisor" action until it does know one. That way, we are able to spawn large amounts of wallets

src/main/java/fucoin/actions/join/ActionJoinAnswer.java

@@ -2,9 +2,13 @@ package fucoin.actions.join;
 
 import akka.actor.ActorRef;
 import akka.actor.UntypedActorContext;
+import akka.dispatch.OnSuccess;
 import fucoin.actions.ClientAction;
 import fucoin.actions.persist.ActionSearchMyWallet;
 import fucoin.wallet.AbstractWallet;
+import scala.Function1;
+import scala.concurrent.Future;
+import scala.runtime.BoxedUnit;
 
 import java.util.HashMap;
 import java.util.Map.Entry;