Finds and returns an edge between value-or-vertex-1
and value-or-vertex-2 if one exists. Unless error-if-not-found? is
nil, then a error will be signaled. [?? Error not signal, need
test.]
| find-edge-between-vertexes-if < graph-container > < graph-container-vertex > < graph-container-vertex > < t > |
| find-edge-between-vertexes-if < graph-container > < t > < t > < t > |