Add support for specific random graph generators
Add support for generation of some specific, but commonly used, random graphs:
- [http://en.wikipedia.org/wiki/Preferential_attachment Barabási-Albert] networks (undirected)
- [http://www.garfield.library.upenn.edu/papers/pricenetworks1965.pdf Price network] (directed)
- Erdős-Reyni graphs (can be just an alias to the specific parameters of the general correlated configurational model)
- [http://en.wikipedia.org/wiki/Watts_and_Strogatz_model Watts-Strogatz] small world network
- ...