Log actor failures in supervisor, see #2824

* To make it possible to override with application
  specific logging, or mute logging for certain failures
* Changed log level of Resume failures to WARNING, which
  caused all the changes to the tests

akka-docs/rst/java/fault-tolerance.rst

@@ -52,6 +52,13 @@ restarts per minute. ``-1`` and ``Duration.Inf()`` means that the respective lim
 does not apply, leaving the possibility to specify an absolute upper limit on the
 restarts or to make the restarts work infinitely.
 
+.. note::
+
+  If the strategy is declared inside the supervising actor (as opposed to
+  a separate class) its decider has access to all internal state of
+  the actor in a thread-safe fashion, including obtaining a reference to the
+  currently failed child (available as the ``getSender`` of the failure message).
+
 Default Supervisor Strategy
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -78,6 +85,22 @@ loss of the child. This strategy is also provided pre-packaged as
 :class:`StoppingSupervisorStrategy` configurator to be used when you want the
 ``"/user"`` guardian to apply it.
 
+Logging of Actor Failures
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+By default the ``SupervisorStrategy`` logs failures unless they are escalated.
+Escalated failures are supposed to be handled, and potentially logged, at a level
+higher in the hierarchy.
+
+You can mute the default logging of a ``SupervisorStrategy`` by setting
+``loggingEnabled`` to ``false`` when instantiating it. Customized logging
+can be done inside the ``Decider``. Note that the reference to the currently
+failed child is available as the ``getSender`` when the ``SupervisorStrategy`` is
+declared inside the supervising actor.
+
+You may also customize the logging in your own ``SupervisorStrategy`` implementation
+by overriding the ``logFailure`` method.
+
 Supervision of Top-Level Actors
 -------------------------------
 

akka-docs/rst/java/untyped-actors.rst

@@ -739,7 +739,7 @@ Please note, that the child actors are *still restarted*, but no new ``ActorRef`
 the same principles for the children, ensuring that their ``preStart()`` method is called only at the creation of their
 refs.
 
-For more information see :ref:`what-restarting-means-scala`.
+For more information see :ref:`supervision-restart`.
 
 Initialization via message passing
 ----------------------------------