Re-enable akka-kernel and add small sample

Created a new simple version of the microkernel for
inclusion in the akka download and to be able to start
working on sample applications

akka-samples/akka-sample-hello-kernel/src/main/config/akka.conf

@@ -0,0 +1,8 @@
+# Config for the Hello Kernel sample
+
+akka {
+  kernel {
+  	system.name = "hellokernel"
+  	boot = ["sample.kernel.hello.HelloKernel"]
+  }
+}

akka-samples/akka-sample-hello-kernel/src/main/scala/sample/kernel/hello/HelloKernel.scala

@@ -0,0 +1,33 @@
+/**
+ *  Copyright (C) 2009-2011 Typesafe Inc. <http://www.typesafe.com>
+ */
+package sample.kernel.hello
+
+import akka.actor.{ Actor, ActorSystem, Props }
+import akka.kernel.Bootable
+
+case object Start
+
+class HelloActor extends Actor {
+  val worldActor = context.actorOf(Props[WorldActor])
+
+  def receive = {
+    case Start ⇒ worldActor ! "Hello"
+    case message: String ⇒
+      println("Received message '%s'" format message)
+  }
+}
+
+class WorldActor extends Actor {
+  def receive = {
+    case message: String ⇒ sender ! (message.toUpperCase + " world!")
+  }
+}
+
+class HelloKernel extends Bootable {
+  def startup(system: ActorSystem) = {
+    system.actorOf(Props[HelloActor]) ! Start
+  }
+
+  def shutdown(system: ActorSystem) = {}
+}