* and rename the factory for ActorPublisherSource,
from Source.apply to Source.actorPublisher
* including internal buffer, with OverflowStrategy
* support to complete/fail stream
* FlowMaterializer is now the actor independent interface
* ActorFlowMaterializer is the actor based interface
* MaterializerSettings renamed to ActorFlowMaterializerSettings
* impl.ActorBasedFlowMaterializer renamed to impl.ActorFlowMaterializerImpl
* Optimizations included in ActorFlowMaterializerSettings
* Note that http is using FlowMaterializer in api, but I suspect that it
will currently only run with a ActorFlowMaterializer
