+str #15085 Add Duct as free-standing Flow
+str #15084 Use sensible flow processor actor names
+str #15093 Add flow logging facility

* Fixes #15093
* Add Transformer.onError
Merge pull request #15151 from akka/wip-15084-stream-actor-names-patriknw

#15084 flow actor names, #15093 logging facility
Merge pull request #15143 from akka/wip-15085-duct-patriknw

+str #15085 Add Duct as free-standing Flow