Implement other sample graph types

[csmangum]

• Small-World Graph Description: A graph characterized by short path lengths and high clustering, often generated by the Watts-Strogatz model. Use Cases: Social network analysis and the study of efficient communication networks.
• Multigraph Description: A graph where multiple edges (parallel edges) can exist between the same set of vertices. Use Cases: Transportation networks and network reliability studies.
• Hypergraph Description: A generalization of a graph where an edge (called a hyperedge) can connect any number of vertices. Use Cases: Representing complex relationships in data sets, such as database modeling and VLSI design.