Double counting edge weight bug fix.

[qnzhou]

Summary:

• In simple_graph_cut function, when multiple edges are connecting the same nodes (i.e. an arrangement cell is adjacent to another cell at multiple places), their weights are summed in hPair but they are inserted into the graph multiples times with the summed weight. This leads to incorrect result in corner cases.
• The fix is to combine those edge into one with the summed weight and insert it only once in the graph.
• Update dependencies so it compiles.

A minimal example: cell c0 and c1 interface at 2 different patches (green and blue). So there are two edges connecting c0 and c1 in the graph.