Add offset value to edges

[CalNightingale]

Handles edge case where two edges share the same port - they are parallel and overlapping for some portion of their length at the moment. On edge creation, at the end, call station.resolveOverlaps(). This function should check the quantity of edges using each port. If there are 2+ edges, set offset values accordingly. Which edge should be offset in which direction can be determined by comparing the positions (x and y) of the other stations each edge connects to.