=str #15250 Use BlackholeConsumer for Flow.consume()

* last operator in front of consume() was treated specially, running
  in impl.ActorConsumer instead of the ordinary processors
=str Change to testkit jar dependency
+pro,doc #15290 Add separate doc project for release-2.3-dev

* Create sepaate project for stream and http docs.
* Make validatePullRequest run the relevant tests only.
Merge pull request #15294 from akka/wip-15290-split-up-doc-projects-ban

+pro,doc #15290 Add separate doc project for release-2.3-dev
str =15252 Add dsl consistency spec
incorporate feedback
Merge pull request #15258 from akka/wip-15252-dsl-consistency-patriknw

str =15252 Add dsl consistency spec
=str #15253 Check for null exposed pub in stop
Merge pull request #15260 from akka/wip-15253-npe-patrikw

=str #15253 Check for null exposed pub in stop
=str #15242 Add test for converting onComplete to onError
Merge pull request #15267 from akka/wip-15242-onComplete-onError-patriknw

=str #15242 Add test for converting onComplete to onError
Merge pull request #15259 from akka/wip-15250-blackhole-consumer-patriknw

=str #15250 Use BlackholeConsumer for Flow.consume()
Merge pull request #15282 from akka/wip-testkit-dep-patriknw

=str Change to testkit jar dependency
+str #15218 Add mapFuture operator
propagate future failure immediately