Bye-bye ReflectiveAccess, introducing PropertyMaster, see #1750

- PropertyMaster is the only place in Akka which calls
  ClassLoader.getClass (apart from kernel, which might be special)
- all PropertyMaster methods (there are only three) take a ClassManifest
  of what is to be constructed, and they verify that the obtained object
  is actually compatible with the required type

Other stuff:
- noticed that I had forgotten to change to ExtendedActorSystem when
  constructing Extensions by ExtensionKey (damn you, reflection!)
- moved Serializer.currentSystem into JavaSerializer, because that’s the
  only one needing it (it’s only used in readResolve() methods)
- Serializers are constructed now with one-arg constructor taking
  ExtendedActorSystem (if that exists, otherwise no-arg as before), to
  allow JavaSerializer to do its magic; possibly necessary for others as
  well
- Removed all Option[ClassLoader] signatures
- made it so that the ActorSystem will try context class loader, then
  the class loader which loaded the class actually calling into
  ActorSystem.apply, then the loader which loaded ActorSystemImpl
- for the second of the above I added a (reflectively accessed hopefully
  safe) facility for getting caller Class[_] objects by using
  sun.reflect.Reflection; this is optional an defaults to None, e.g. on
  Android, which means that getting the caller’s classloader is done on
  a best effort basis (there’s nothing we can do because a StackTrace
  does not contain actual Class[_] objects).
- refactored DurableMailbox to contain the owner val and use that
  instead of declaring that in all subclasses

akka-docs/java/code/akka/docs/serialization/SerializationDocTestBase.java

@@ -3,6 +3,7 @@
  */
 package akka.docs.serialization;
 
+import akka.japi.Option;
 import akka.serialization.JSerializer;
 import akka.serialization.Serialization;
 import akka.serialization.SerializationExtension;
@@ -13,6 +14,7 @@ import static org.junit.Assert.*;
 
 import akka.serialization.*;
 import akka.actor.ActorSystem;
+import akka.actor.PropertyMaster;
 import com.typesafe.config.*;
 
 //#imports
@@ -45,8 +47,7 @@ public class SerializationDocTestBase {
       // using the type hint (if any, see "includeManifest" above)
       // into the optionally provided classLoader.
       @Override public Object fromBinary(byte[] bytes,
-                     Class clazz,
-                     ClassLoader classLoader) {
+                     Class clazz) {
         // Put your code that deserializes here
         //#...
         return null;
@@ -128,7 +129,7 @@ public class SerializationDocTestBase {
 
       // Turn it back into an object,
       // the nulls are for the class manifest and for the classloader
-      String back = (String)serializer.fromBinary(bytes);
+      String back = (String)serializer.fromBinary(bytes, Option.<Class<?>>none().asScala());
 
       // Voilá!
       assertEquals(original, back);