Add Raiyan's edge weighted algorithm work

[mtorpey]

Raiyan did a bunch of good work on edge-weighted algorithms, which was made into PR #584.

My latest version of this work is at
https://github.com/mtorpey/Digraphs/tree/edge-weight-algorithms from which I'm making PRs one bit at a time.

Approximate todo list:

• EdgeWeightedDigraphMinimumSpanningTree: Edge-weights #3: minimum spanning trees #650
• DigraphEdgeWeightedShortestPath[s]: Edge weights #4: shortest path(s) #656
• DigraphMaximumFlow/DigraphMinimumCuts: Edge weights #5: maximum flow #751
• RandomUniqueEdgeWeightedDigraph: Edge weights #6: RandomUniqueEdgeWeightedDigraph #755
• Random strongly connected digraph (semi-related): Abstract RandomDigraphCons redirect methods #871
• DotEdgeWeightedDigraph: Edge weights #7: DotEdgeWeightedDigraph #892