+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/doc/LambdaPersistencePluginDocTest.java

@@ -0,0 +1,113 @@
+/**
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package doc;
+
+//#plugin-imports
+import akka.japi.pf.ReceiveBuilder;
+import scala.PartialFunction;
+import scala.concurrent.Future;
+import akka.japi.Option;
+import akka.japi.Procedure;
+import akka.persistence.*;
+import akka.persistence.journal.japi.*;
+import akka.persistence.snapshot.japi.*;
+//#plugin-imports
+import akka.actor.*;
+import akka.persistence.journal.leveldb.SharedLeveldbJournal;
+import akka.persistence.journal.leveldb.SharedLeveldbStore;
+import scala.runtime.BoxedUnit;
+
+public class LambdaPersistencePluginDocTest {
+
+
+  static Object o1 = new Object() {
+    final ActorSystem system = null;
+    //#shared-store-creation
+    final ActorRef store = system.actorOf(Props.create(SharedLeveldbStore.class), "store");
+    //#shared-store-creation
+
+    //#shared-store-usage
+    class SharedStorageUsage extends AbstractActor {
+      @Override
+      public void preStart() throws Exception {
+        String path = "akka.tcp://example@127.0.0.1:2552/user/store";
+        ActorSelection selection = context().actorSelection(path);
+        selection.tell(new Identify(1), self());
+      }
+
+      @Override public PartialFunction<Object, BoxedUnit> receive() {
+        return ReceiveBuilder.
+            match(ActorIdentity.class, ai -> {
+              if (ai.correlationId().equals(1)) {
+                ActorRef store = ai.getRef();
+                if (store != null) {
+                  SharedLeveldbJournal.setStore(store, context().system());
+                }
+              }
+            }).build();
+      }
+    }
+    //#shared-store-usage
+  };
+
+  class MySnapshotStore extends SnapshotStore {
+    @Override
+    public Future<Option<SelectedSnapshot>> doLoadAsync(String processorId, SnapshotSelectionCriteria criteria) {
+      return null;
+    }
+
+    @Override
+    public Future<Void> doSaveAsync(SnapshotMetadata metadata, Object snapshot) {
+      return null;
+    }
+
+    @Override
+    public void onSaved(SnapshotMetadata metadata) throws Exception {
+    }
+
+    @Override
+    public void doDelete(SnapshotMetadata metadata) throws Exception {
+    }
+
+    @Override
+    public void doDelete(String processorId, SnapshotSelectionCriteria criteria) throws Exception {
+    }
+  }
+
+  class MyAsyncJournal extends AsyncWriteJournal {
+    @Override
+    public Future<Void> doAsyncWriteMessages(Iterable<PersistentRepr> messages) {
+      return null;
+    }
+
+    @Override
+    public Future<Void> doAsyncWriteConfirmations(Iterable<PersistentConfirmation> confirmations) {
+      return null;
+    }
+
+    @Override
+    public Future<Void> doAsyncDeleteMessages(Iterable<PersistentId> messageIds, boolean permanent) {
+      return null;
+    }
+
+    @Override
+    public Future<Void> doAsyncDeleteMessagesTo(String processorId, long toSequenceNr, boolean permanent) {
+      return null;
+    }
+
+    @Override
+    public Future<Void> doAsyncReplayMessages(String processorId, long fromSequenceNr,
+                                              long toSequenceNr,
+                                              long max,
+                                              Procedure<PersistentRepr> replayCallback) {
+      return null;
+    }
+
+    @Override
+    public Future<Long> doAsyncReadHighestSequenceNr(String processorId, long fromSequenceNr) {
+      return null;
+    }
+  }
+}