integrate NetworkFailureInjector and add first test

- rework socket pipeline to transform protobuf into case classes and
  back
- introduce NetworkOp messages for that purpose
- make API asynchronous (because it is, really) and add Done
  notification for all server operations; enter(...) is still
  synchronous, because that is its only purpose in life
- factor out mkPipeline in NettyRemoteTransport, enabling the very slick
  TestConductorTransport (essentially a one-liner)
- switch NetworkFailureInjector from Channel{Up,Down}streamHandler to
  subclassing SimpleChannelHandler, because otherwise deadlocks
  occurred, not sure why (but SCH is the recommended way from the netty
  docs, so there may well be a reason)

akka-remote/src/main/scala/akka/remote/netty/Server.scala

@@ -30,14 +30,12 @@ class NettyRemoteServer(val netty: NettyRemoteTransport) {
     Executors.newCachedThreadPool(netty.system.threadFactory),
     Executors.newCachedThreadPool(netty.system.threadFactory))
 
-  private val executionHandler = new ExecutionHandler(netty.executor)
-
   // group of open channels, used for clean-up
   private val openChannels: ChannelGroup = new DefaultDisposableChannelGroup("akka-remote-server")
 
   private val bootstrap = {
     val b = new ServerBootstrap(factory)
-    b.setPipelineFactory(makePipeline())
+    b.setPipelineFactory(netty.mkPipeline(new RemoteServerHandler(openChannels, netty), false))
     b.setOption("backlog", settings.Backlog)
     b.setOption("tcpNoDelay", true)
     b.setOption("child.keepAlive", true)
@@ -45,8 +43,6 @@ class NettyRemoteServer(val netty: NettyRemoteTransport) {
     b
   }
 
-  protected def makePipeline(): ChannelPipelineFactory = new RemoteServerPipelineFactory(openChannels, executionHandler, netty)
-
   @volatile
   private[akka] var channel: Channel = _
 
@@ -79,26 +75,6 @@ class NettyRemoteServer(val netty: NettyRemoteTransport) {
   }
 }
 
-class RemoteServerPipelineFactory(
-  val openChannels: ChannelGroup,
-  val executionHandler: ExecutionHandler,
-  val netty: NettyRemoteTransport) extends ChannelPipelineFactory {
-
-  import netty.settings
-
-  def getPipeline: ChannelPipeline = {
-    val lenDec = new LengthFieldBasedFrameDecoder(settings.MessageFrameSize, 0, 4, 0, 4)
-    val lenPrep = new LengthFieldPrepender(4)
-    val messageDec = new RemoteMessageDecoder
-    val messageEnc = new RemoteMessageEncoder(netty)
-
-    val authenticator = if (settings.RequireCookie) new RemoteServerAuthenticationHandler(settings.SecureCookie) :: Nil else Nil
-    val remoteServer = new RemoteServerHandler(openChannels, netty)
-    val stages: List[ChannelHandler] = lenDec :: messageDec :: lenPrep :: messageEnc :: executionHandler :: authenticator ::: remoteServer :: Nil
-    new StaticChannelPipeline(stages: _*)
-  }
-}
-
 @ChannelHandler.Sharable
 class RemoteServerAuthenticationHandler(secureCookie: Option[String]) extends SimpleChannelUpstreamHandler {
   val authenticated = new AnyRef