* Provide shorter aliases for the ActorRefProviders #20649
* Use the new actorefprovider aliases throughout code and docs
* Cleaner alias replacement logic
* In 2.4 we derive the number of hand-over/take-over retries from
the removal margin, but we decided to set that to 0 by default, since
it is intended for network partition scenarios. maxTakeOverRetries
became 1. So there must be also be a min number of retries property.
* The test failed for the leaving scenario because the singleton
instance was stopped hard without sending the terminationMessage when
the maxTakeOverRetries was exceeded.
