Fixes #5984 by having ED-209s now pass through each other.

ED-209s now pass through each other, unless walking in the same direction to avoid position shuffling behavior. 
Still haven't forgotten about the whole copy-paste issue.
The original thought was I wouldn't want ED-209 to occasionally receive a tiny boost by crossing paths with Beepsky or other bots.
After this comment I gave the matter some more thought and realized that this is a non-issue for bots with a density of 0 since bump won't be called anyway.