Calculates the step in the opposite direction from the provided object.
/proc/get_step_away(/atom/movable/Ref, /atom/Trg, Max)
Arguments:
Ref (/atom/movable): The moving object.
Trg (/atom): The object being moved away from.
Max = 5: The maximum distance between Ref and Trg.
Returns:
/turf, num: The new position; or 0 if no movement has occured.
