[Drawkit] Now with added testing. (was Re: For the brave ; -)

[Graham Cox]

Just FYI: I just did a quick comparison of the route finder versus a  
simple sort of x and y versus manual placement. The grid is regular  
but diagonally offset so that the visitation order for the simple sort  
is clear (this does increase the path lengths slightly but the same  
arrangement was used in all tests). I think it shows that a naive sort  
is pretty useless for this.

If you know in advance that your objects are in a grid arrangement,  
then you'd think you'd be able to come up with a visitation order that  
is better than the route finder - but given a set of arbitrarily  
placed objects, the problem becomes how to detect they are in a grid  
in the first place. However, by manually placing the objects in a  
specific order and doing no sorting at all, (bottom image) the path  
length is *worse* than the route finder! So intuition isn't always  
correct.

Straight sort of Y, then X: (path length 9896.748047)

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DKRouteFinder: (path length 4810.483887)

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Manually placed and unsorted: (path length 5210.396973)

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