=str #16085 PublisherSink is no longer a singleton

* rename existing Source/Sink tests to the latest names
* uncomment TickSource test with Zip
=htp enable tests that were erroneously disabled due to specs2 -> scalatest copy-pasta
=htp small improvement to Marshaller
!htp #15935 clean up and extend unmarshalling infrastructure
+htp #15929 port ParameterDirectives from spray
Merge pull request #16094 from spray/wip-15929-mathias

Import ParameterDirectives from spray
Merge pull request #16108 from spray/w/port-more-directives

Fixes for 15931, 15918, 15919
Merge pull request #16111 from 2m/wip-unsingle-publisher-drain

=str #16085 PublisherSink is no longer a singleton
=str #16103 Flattened javadsl class structure - no adapters, no ops
Merge pull request #16107 from ktoso/wip-cleanup-javadsl-ktoso

=str #16103 Flattening FlowOps into Flow (same for Sink / Source)
=str #16109 Workaround scalax.graph reflection issue
+str #16077 implement Zip/Unzip/Concat for javadsl, while reusing all impl
+str #16046 implemented OverflowStrategy.error
Merge pull request #16118 from ktoso/wip-error-overflowstrategy-ktoso

+str #16046 implemented OverflowStrategy.error
Merge pull request #16110 from ktoso/wip-fan-ops-javadsl-ktoso

+str #16077 implement Zip/Unzip/Concat for javadsl
Merge pull request #16120 from akka/wip-16109-workaround-patriknw

=str #16109 Workaround scalax.graph reflection issue
=str #16095 make Actor{Publisher,Subscriber} as {Source,Sink}

* Props{Source,Sink} creates an actor from props as a child
of StreamSupervisor actor and wraps it into {Publisher,Subscriber}.
Actor should be one of akka.stream.actor.Actor{Publisher,Subscriber}
=str #16041 Move PersistentSource to the latest Stream DSL

* implemented as an extension of KeyedActorFlowSource
Merge pull request #16119 from 2m/wip-actor-pub-sub-source-sink-16095

=str #16095 make Actor{Publisher,Subscriber} as {Source,Sink}
Merge pull request #16133 from 2m/wip-persistent-source-16041

=str #16041 Move PersistentSource to the latest Stream DSL