Changed Failed to be a SystemMessage

- Moved system messages to their own package.
 - All queueing operations are now hidden behind a SystemMessageList value class
 - Introduced dual SystemMessageList types to encode the ordering in the type.
   - Protects against accidentally missed reverse calls or accidentally reversed lists
   - Makes ordering expectations by fields/parameters explicit
 - Fixed serialization tests
 - Fixes to logging in HierarchyStressSpec

akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala

@@ -5,7 +5,7 @@
 package akka.remote
 
 import akka.actor._
-import akka.dispatch._
+import akka.dispatch.sysmsg._
 import akka.event.{ Logging, LoggingAdapter, EventStream }
 import akka.event.Logging.Error
 import akka.serialization.{ JavaSerializer, Serialization, SerializationExtension }