Enabled Using Repartitioned Graphs, Added Display

[dlcole3]

This PR address three minor problems

• The get_upper_bounds function when monotonic = true would only return a one element vector because a parenthesis was in the wrong place
• If a graph was formed via the induce_subgraph command in Plasmo, the constructor function would error at initialization. I changed how it determines the linking variables. This was previously a bottleneck point because it was calling union or intersect and was replaced by calling source_graph on a node (see Re-structure single graph model for Benders algorithm #25). I think the new method is roughly as efficient as the source_graph method, and some preliminary benchmarking suggests this is the case.
• Base.show and Base.print were not implemented for the BendersAlgorithm. For large problems, the display in the REPL was really clunky and not helpful, so this PR adds a display ability.