Duplo Technic Gears

This recreates the three standard gear sizes used in Duplo Technic and adds some in-between sizes for potential use with diagonals. Based on [gear-v3.scad by mrob27](https://www.thingiverse.com/thing:40410) with some major modification to make it work well with [printed Duplo Technic axles](https://www.thingiverse.com/thing:3416238).

Official parts (somewhat) recreated:
* [6523 DACTA GEAR WHEEL Z8/AXLE](https://brickset.com/parts/design-6523) without the axle
* [6529 DACTA GEAR WHEEL Z24, M