=doc First draft of Streams design principles
=doc add section on Error vs. Failure for streams

… and some more clarifications after review.
=doc add section on three-phased stream materialization
=str #16259 Added more red-face testing of the stream Java DSL
=str Ensure the visibility of the DelayedInitProcessor implementation var
=doc clarify that onError is for failures (d’oh)
Merge pull request #16446 from akka/wip-16259-stream-javadsl-tests-ban

=str #16259 Added more redface testing of the stream Java DSL
=pro add missing versions
Merge pull request #16419 from akka/wip-stream-design-docs

=doc First draft of Streams design principles
Merge pull request #16447 from akka/wip-ensure-visibility-of-dealyed-init-processor-impl-ban

=str Ensure the visibility of the DelayedInitProcessor implementation var
Merge pull request #16449 from 2m/wip-fix-project-versions

=pro add missing versions
=htt #16452 rename java8 http sample
Merge pull request #16453 from 2m/wip-16452-java8-server-app

=htt #16452 rename java8 http sample
+str - adds ZipWith and makes Zip use that to create tuples/pairs