Update Stacking Lip Profile

[EmperorArthur]

Profile is now based on https://gridfinity.xyz/specification/ This does not change the final profile, merely how it is created.

Fixes #168 - Cura watertight issue. Fixes #169 - FreeCad errors.

Edit: Also Fixes #165

[EmperorArthur]

Much larger than the last one, but hopefully I've commented enough to show how everything works. Feel free to ask questions.

Shape was verified in multiple ways:

• Overlapping the new 2d over the old, with a 1mm Z translate and manually examining them.
• Examining the 2d shape and 3d wall in FreeCad (where possible).
• Examining the 3d wall in Cura.
• 3D printing it

If you like this approach, I may take a shot at re-creating the bases in a similar manner. The sweep function is really neat, and can avoid the need to deal with the annoyances hull() causes.