#3272: Eliminate redundant 'should' in DataflowSpec test
Merge remote-tracking branch 'upstream/master'
fix ActorSelection hashCode/equals and ask, see #3287 #3261
Merge remote-tracking branch 'upstream/master'
remove NullMessage, see #3281
Cluster member age, and usage in singleton, see #3195

* Assign internal upNumber when member is moved to Up
* Public API Member.isOlder
* Change cluster singleton to use oldest member instead of leader
* Update samples and docs
call executor.prepare() for scheduled jobs, see #3307
Merge remote-tracking branch 'upstream/master'
Merge pull request #1383 from akka/wip-3195-member-age-patriknw

Cluster member age, and usage in singleton, see #3195
Logging of the size of different message types.

* Maximum detected size per message type is logged once
* Default configuration disables this feature
Merge branch 'wip-3281-NullMessage-∂π'
Merge pull request #1400 from akka/wip-3307-prepare-EC-∂π

call executor.prepare() for scheduled jobs, see #3307
remove ActorRef#tell(Any), see #3293

also remove FakeActorRef from SerCompSpec
Merge pull request #1389 from akka/wip-3287-actorSelection-∂π

ActorSelection: equals/hashCode and “ask”
Changed design of RemoteWatcher due to cleanup race, see #3265

* The problem was a race caused by HeartbeatReq sent out, and
  the watchee terminated immediately. That caused the RemoteWatcher
  peers watching each other without any other watch registered.
  It is racy.
* Instead of one-way heartbeats from the side beeing watched I
  changed to ping-pong style. That makes the problem go away
  and simplifies a lot of things in RemoteWatcher.
Merge pull request #1396 from akka/wip-3293-remove-single-arg-tell-∂π

remove ActorRef#tell(Any), see #3293
Merge pull request #1385 from akka/wip-3280-log-payload-size-patriknw

Logging of the size of different message types.
Wait on shutdown of extra actor systems in tests. See #3217
Merge pull request #1395 from akka/wip-3217-remotedeathwatchspec-failure-ban

Wait on shutdown of extra actor systems in tests. #3217
Actor fields are cleared after Terminated is sent. See #3311