* Add supervisor level that will start the ShardCoordinator again after
a configurable backoff duration
* Make the timeout of SharedLeveldbJournal configurable
* Include cause of PersistenceFailure in message of ActorKilledException
* The problem was that ShardRegion actor only kept track of one shard
id per region actor. Therefore the Terminated message only removes
one of the shards from its registry when there are multiple shards
per region.
* Added failing test and solved the problem by keeping track of all
shards per region
* Also, rebalance must not be done before any regions have been
registered
* because it is not referentially transparent; normally we reserved parens for
side-effecting code but given how people thoughtlessly close over it we revised
that that decision for sender
* caller can still omit parens
- removed retry-window and related settings
- removed gate-invalid-addresses-for
- gate is now mandatory
- remoting has a dedicated dispatcher by default
- updated tests to work with changed timings
- added doc section for association lifecycle
