Network edge count/iter performance testing

[etatara]

The networkx graph API for getting the in and out edges appear to be costly, e.g.:

in_count = len(self.network.graph.in_edges(person))
out_count = len(self.network.graph.in_edges(person))

are pretty slow for large networks (30,000 nodes and 15,000 edges). We should investigate if there are
more efficient API calls in networkx that provide edge counts, and edge views in general, as in iterating over
agent network edges like

donor_list = [x for x,_ in self.network.graph.in_edges(self)]

Furthermore, we might want to provide repast4py network API for these functions so the user doesn't need to reference the underlying networkx graph.