Remove start node search algo class
Add clear methods to path length data
Refactor: make analyzers create fewer objects.

This also cleans up the GraphAnalyzer class.

Now the algorithms' calculate methods have a start node.

I am seeing better performance time in BFS (e.g., Nantes 2:52 -> 2:15)
but worse for Dijkstra (2:06 -> 2:27).
Update tests