Fix polygons getting thicker

[u1f992]

#134 This is most noticeable in the last image on previous PR, where each of the polygon paths has "padding" that extends outward from expected. I found that for small footprints, this difference results in margin overlapping. We can avoid this problem by setting the width of each path to 0.

Current	This PR

However, as we can see, the pad minimized in the previous PR appears as a small circle in the polygon's center. I am working on a way to remove this.

[u1f992]

One inelegant idea is to check if the anchor pad's circle is encapsulated within the polygon. If it is not, move the anchor pad so that it is encapsulated within the polygon, while maintaining the absolute coordinates of all polygon vertices.

[u1f992]

It took a lot of geometric functions, but it seems to be working initially. The absolute position of the pad is not changed, and the new center point (the small anchor pad position) moved to the intersection. It turned out to be not so 'without too much code modifications' after all, didn't it :-}