Implemented AllPairsShortestPath routine using Johnson algorithm (i.e. one execution of Bellman-Ford algorithm+N executions of Dijkstra's algorithm);
Fixed bug in ShortestPathUsingBellmanFord function (we say that there is a negative cycle when counter variable for the number of iterations i==N-1,
not i==N);
Finally added a possibility to load graph from file in testSimpleGraph program and added the possibility to test newly added functionality;
Added few more test graph files.