v1.2.1

• Improved slot shape for N-6
• Added expansion of rim_slope to dynamically accommodate larger seed holes
• Added prototoype J#-6 series and "finger" shape
• Hoisted bore calculation to bore
• Switched from polyhedron() to linear_extrude() polygon() for future ImplicitCAD use
• Minor lint fixes for ImplicitCAD (which is far tetchier about dangling commas, and drops very confusing errors when you have 'em)
• Improved rendering speed over 1.1
• Dropped MCAD
• Improved labels over 1.1
• Sorted preset names alphabetically (same order they'll appear in the filesystem)