1) better documentation of all how the xy placement file is calculated. also, the source code mentions that unnumbered pins are left out of the calculation, which should be clearly documented (if it's in the manual right now, it's not as loudly stated as it probably should be, because I don't remember coming across it).
actually, I think that comment is misleading. unnumbered pins are not left out. I'll fix that too.
-Dan
