akka/akka — pull request #15597 by DomBlack (2014-07-28 14:43:43+00:00)
Title: !con #15496 Make entries of shards persistent

- Move all entry related logic out of the ShardRegion and into a
new dedicated child `Shard` actor.
- Shard actor persists entry started and passivated messages.
- Non passivated entries get restarted on termination.
- Shard Coordinator restarts shards on other regions upon region failure or handoff
- Ensures shard rebalance restarts shards.