Remove old file
Remove add_to_vnames/enames/bboxes from graph structures

These are just confusing, as they look like graph mutators but are not,
and only use in debug code (where they are trivial to replicate).
Remove unused functions

Using these is likely to break the graph.
Raise ex in edge_get_other_vertex if given a vertex not on the edge
Consider edge directedness in Graph.exact_eq
More consistent test coverage for Graph interface.
Convert !-graph tests to new test graph type