generate toolpath

[tmpvar]

using the same techniques seen at http://tmpvar.com/tmp/poly/tree.html

• [x] slice mesh (starting at top for milling)
• [x] offset resulting polygons
• [x] holes are inset
• [x] contours are outset
• [x] xor the results
• [x] union the results

[tmpvar]

this is functional but has degenerate cases. those will be tracked on a case by case basis