* Merged layer_producer and channel_producer from 2.0 to the reroute module (replacin...

* Merged layer_producer and channel_producer from 2.0 to the reroute module (replacing the existing implementation).
* In order to support route:// without the same intrusive changes in AMCPCommandsImpl.cpp from 2.0, refactored so that every producer factory gets a list of channels.
* Refactored so that frame_factory and video_format_desc is now part of a type called frame_producer_dependencies. The list of channels needed by reroute producer was also added to this class. Future dependencies will not need a change in the signature of every producer factory.
* Fixed possible race condition in stage.cpp where std::map could be modified from multiple threads