* changing Plugin API for asyncWriteMessages and writeMessages
* passing explicit AtomicWrite that represents the events of
persistAll, or a single event from persist
* journal may reject events before storing them, and that
will result in onPersistRejected (logging) and continue in the
persistent actor
* clarified the semantics with regards to batches and atomic writes,
and failures and rejections in the api docs of asyncWriteMessages
and writeMessages
* adjust the Java plugin API, asyncReplayMessages, doLoadAsync
8c47e01e9d