* The reason is to have a consistent approach for Sequence and
TimeBasedUUID, which are both intended as unique event identifiers.
* This means that you can use the offset that is returned in `EventEnvelope`
as the `offset` parameter in a subsequent query.
This entails:
* adding akka.pattern.PatternCS.* to enable ask etc. with
CompletionStage
* changing RequestContext to offer an ExecutionContextExecutor for the
CompletionStage.*Async combinators
* splitting up akka.stream.Queue for JavaDSL consistency
* make the standard queries "single method interfaces" that may be implemented
by a query journal plugin
* remove hints (major problems with varargs anyway), the hints for standard
queries should be given in configuration instead, e.g. refresh-interval