Added small library of sample graphs

This can conveniently be added in basic tests.
Enumerations of more complex graphs are to be added.
Added benchmark class of graph isomorphism

Useful for benchmarking certain implementation details
Updated Edge class to not allow loops

This library is concerned with simple graphs (no loops)
therefor an edge from a vertice to itself is illegal.
overriden Graph.toString to display order and edges
Tested and fixed shattering in graph.iso

Added first tests for shattering function and fixed
some bugs. Also made the implementation slightly more
efficient.