Documentation improvements

* Re enabling Java tests in akka-docs (they were not run before)
* Fixed bug #19764
* #19735 Rewrote every sample using the deprecated PushPullStage and friends
  using GraphStage
* Pruned old unused graph images
* Added missing graffle file for new graph images

akka-docs/rst/java/code/docs/AbstractJavaTest.scala

@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) 2016 Typesafe Inc. <http://www.typesafe.com>
+ */
+package docs
+
+import org.scalatest.junit.JUnitSuite
+
+/**
+ * Base class for all runnable example tests written in Java
+ */
+abstract class AbstractJavaTest extends JUnitSuite {
+
+}