Fix exiting ordering problem in ClusterSingletonManager, see #3408

* The problem was:
  - first is leaving, second is new oldest
  - two actors subscribe to cluster events, OldestChangedBuffer and ClusterSingletonManager
  - ClusterSingletonManager receives MemberExited(first), and then also MemberRemoved(second)
    before OldestChangedBuffer receives MemberExited(first) and delivers
    OldestChanged(first->second)
  - MemberRemoved(second) is the result of the cluster extension shutdown
  - because ClusterSingletonManager gets the MemberRemoved(second) before the OldestChanged
    it will not send the hand over data to second
  - second becomes new singleton after retry period, as designed, but without hand over data
 * The solution is to check the selfExited flag in Oldest state, similar to what is done
   in WasOldest
 * I considered the alternative to tunnel all member events through same subscriber,
   but that would involve more changes to the code
Increase ask timeout in CoordinatedIncrementSpec, see #3409
Dilate ask timeout in ConcurrentActivationTest, see #3413
Footnote breaks pdf generation
Merge pull request #1499 from akka/wip-fix-footnote-patriknw

Footnote breaks pdf generation
Merge pull request #1498 from akka/wip-3413-ConcurrentActivationTest-patriknw

Dilate ask timeout in ConcurrentActivationTest, see #3413
Merge pull request #1497 from akka/wip-3409-CoordinatedIncrementSpec-patriknw

Increase ask timeout in CoordinatedIncrementSpec, see #3409
Merge pull request #1496 from akka/wip-3408-ClusterSingletonManager-leaving-order-patriknw

Fix exiting ordering problem in ClusterSingletonManager, see #3408
OSGi Make the integration test work again. See #3292

OSGi Adding ScalaBuff and removing experimental from cluster. See #3292
OSGi create bundle for ScalaBuff. See #3292
OSGi Make the integration test work again. See #3292
make LocalScope mean “purely local” and avoid Props serialization check, see #3210
improve safety of Props.create by allowing Creator<T>, see #3377

Props constructors need to be deprecated instead of being mutated
because we cannot just start throwing exceptions in people’s existing
code. Props.withCreator is deprecated for similar reasons, but also
because Props are about the creators, so replacing that after the fact
is not good style.
Merge pull request #1490 from akka/wip-3377-Props.create-∂π

improve safety of Props.create by allowing Creator<T>, see #3377
Make AkkaSpec getCallerName work on J9. See #2996
remove unused pom.xml with akka-cluster-experimental ref
Merge pull request #1503 from akka/wip-3292-osgi-integration-test-ban

OSGi Make the integration test work again #3292
Merge pull request #1504 from akka/wip-2996-make-test-work-on-j9-ban

Make AkkaSpec getCallerName work on J9 #2996
Add a barrier in RemoteNodeDeathWatchSpec to compensate for connection time. See #3390
only create the routees once they can be looked-up, see #3406

- move the creation of the RoutedActorCell’s route into
  ActorCell.start(); it used to be done in the constructor
- this requires “val route” to turn into a volatile private var

Thanks to Patrik for finding it!
adapt SchedulerSpec rate test to 10ms time slices, see #3391

using a larger sample will also make the spread of the resulting
calculated rate smaller; the referenced ticket is about a deviation from
the target rate which was slightly out of bounds
Merge pull request #1506 from akka/wip-3390-remotenodedeathwatch-failure-ban

Add a barrier in RemoteNodeDeathWatchSpec to compensate for connection time #3390