+per #3906 add Java8 support for Persistence

- Provided new interfaces for akka-persistence to be usable directly
  through ReceiveBuilder/PartialFunction. Added a sample java project to
  showcase the usage of these API's with akka-persistence.
- Fixed a minor comment block in javadoc code snippet.
- Renamed java event persistor and fixed a documentation typo.
- Put back java event persistence methods in
  UntypedEventsourcedProcessor and copied them into
  AbstractEventsourcedProcessor for the sake of clarity in javadocs.
  Also corrected some doc punctuations.
- Documentation for akka-persistence java 8 lambda expressions support.
- Moved code examples referred from within lambda-persistence.rst to
  java8 compatible sample project.
- Removed remaining unwanted java8 compatible source files.

akka-samples/akka-sample-persistence-java8/src/main/java/sample/persistence/ViewExample.java

@@ -0,0 +1,100 @@
+/**
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package sample.persistence;
+
+import akka.actor.AbstractActor;
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.actor.Props;
+import akka.japi.pf.ReceiveBuilder;
+import akka.persistence.*;
+import scala.PartialFunction;
+import scala.concurrent.duration.Duration;
+import scala.runtime.BoxedUnit;
+
+import java.util.concurrent.TimeUnit;
+
+public class ViewExample {
+    public static class ExampleProcessor extends AbstractProcessor {
+        @Override
+        public String processorId() {
+            return "processor-5";
+        }
+
+        @Override public PartialFunction<Object, BoxedUnit> receive() {
+            return ReceiveBuilder.
+                match(Persistent.class,
+                      p -> System.out.println(String.format("processor received %s (sequence nr = %d)",
+                                                            p.payload(),
+                                                            p.sequenceNr()))).build();
+        }
+    }
+
+    public static class ExampleView extends AbstractView {
+        private final ActorRef destination = context().actorOf(Props.create(ExampleDestination.class));
+        private final ActorRef channel     = context().actorOf(Channel.props("channel"));
+
+        private int numReplicated = 0;
+
+        @Override
+        public String viewId() {
+            return "view-5";
+        }
+
+        @Override
+        public String processorId() {
+            return "processor-5";
+        }
+
+        @Override public PartialFunction<Object, BoxedUnit> receive() {
+            return ReceiveBuilder.
+                match(Persistent.class, p -> {
+                    numReplicated += 1;
+                    System.out.println(String.format("view received %s (sequence nr = %d, num replicated = %d)",
+                                                     p.payload(),
+                                                     p.sequenceNr(),
+                                                     numReplicated));
+                    channel.tell(Deliver.create(p.withPayload("replicated-" + p.payload()), destination.path()),
+                                 self());
+                }).
+                match(SnapshotOffer.class, so -> {
+                    numReplicated = (Integer) so.snapshot();
+                    System.out.println(String.format("view received snapshot offer %s (metadata = %s)",
+                                                     numReplicated,
+                                                     so.metadata()));
+                }).
+                match(String.class, s -> s.equals("snap"), s -> saveSnapshot(numReplicated)).build();
+        }
+    }
+
+    public static class ExampleDestination extends AbstractActor {
+
+        @Override public PartialFunction<Object, BoxedUnit> receive() {
+            return ReceiveBuilder.
+                match(ConfirmablePersistent.class, cp -> {
+                    System.out.println(String.format("destination received %s (sequence nr = %s)",
+                                                     cp.payload(),
+                                                     cp.sequenceNr()));
+                    cp.confirm();
+                }).build();
+        }
+    }
+
+    public static void main(String... args) throws Exception {
+        final ActorSystem system = ActorSystem.create("example");
+        final ActorRef processor = system.actorOf(Props.create(ExampleProcessor.class));
+        final ActorRef view = system.actorOf(Props.create(ExampleView.class));
+
+        system.scheduler()
+            .schedule(Duration.Zero(),
+                      Duration.create(2, TimeUnit.SECONDS),
+                      processor,
+                      Persistent.create("scheduled"),
+                      system.dispatcher(),
+                      null);
+        system.scheduler()
+            .schedule(Duration.Zero(), Duration.create(5, TimeUnit.SECONDS), view, "snap", system.dispatcher(), null);
+    }
+}