+str #15588,#17229 Java 6 Synchronous File Sink / Source

These are synchronous implementations, because we need to be Java 6
  compatible while developing on 2.3.x. However asynchronous
  implementations using AsynchronousFileChannel will come soon for JDK7
  users.

+ ActorPublisher/Subscriber now manage stopping of the actor
+ added documentation on configuring dispatcher for File IO
+ properly handle if source file does not exist
+ file sink / source come with default io dispatcher
> verified no actors are leaking
> exceptions are caught and onErrored properly
+ moved files to akka.stream.io
+ Added OutputStreamSink and InputStreamSource

akka-stream/src/main/scala/akka/stream/impl/Sinks.scala

@@ -3,13 +3,17 @@
  */
 package akka.stream.impl
 
+import java.io.File
 import java.util.concurrent.atomic.AtomicReference
 import akka.actor.{ ActorRef, Props }
+import akka.stream.ActorOperationAttributes.Dispatcher
 import akka.stream.impl.StreamLayout.Module
 import akka.stream.OperationAttributes
 import akka.stream.{ Inlet, Shape, SinkShape }
+import akka.util.ByteString
 import org.reactivestreams.{ Publisher, Subscriber, Subscription }
 import scala.annotation.unchecked.uncheckedVariance
+import scala.collection.immutable
 import scala.concurrent.{ Future, Promise }
 import akka.stream.MaterializationContext
 import akka.stream.ActorFlowMaterializer