=str Add broadcast in the graph traversal
=str Add some more tests of complex broadcast-merge combinations
=str Source/Sink vs SourceVertex/SinkVertex equality

* it must be possible to use PublisherSink (object) at several places in the graph
=str Rename Fan to Junction
Merge pull request #15842 from akka/wip-graph-broadcast-traversal-patriknw

=str Add broadcast in the graph traversal