Provide pipeline_kwargs as a way for easier kwarg access

[CJ-Wright]

It might be nice to have a top level key which presents all the kwargs of the pipeline, maybe with node names or as a big heap. This will allow users (and ES) to access that information without having to go all the way down to the networkx representation of the graph (which could be annoying).

[CJ-Wright]

One problem we could run into with a giant dict of kwargs is that they could overlap and then we might loose information (although it is still safe in the graph). If we have the kwargs broken up by node (with maybe a human readable name?) then we are sure that we have the information. I don't know how this squares with the ES work @pavoljuhas @stuartcampbell thoughts?