Finds a dominating set for the graph G.
A dominating set for a graph is a node subset of such that every node not in is adjacent to at least one member of .
- G (NetworkX graph) –
- start_with (Node (default=None)) – Node to use as a starting point for the algorithm.
D – A dominating set for G.
This function is an implementation of algorithm 7 in  which finds some dominating set, not necessarily the smallest one.
 http://en.wikipedia.org/wiki/Dominating_set  Abdol-Hossein Esfahanian. Connectivity Algorithms. http://www.cse.msu.edu/~cse835/Papers/Graph_connectivity_revised.pdf