Sprocket generator OpenSCAD

Remixed "parametric sprockets" a bit.

Now you can easily make idler sprockets.

You can find roller chain specifications here:
https://www.hitachi-metals-techno.com/products/chain/pdf/bs_roller.pdf

Updates

1. Unfortuntatelly Customizer does not recognize sprocket object, so I had to turn it off.
2. Increased cylinder resolution. Faces now are smoother.
3. BUGFIX - cylinder diameters, were interpreted as radiuses
4. BUGFIX - sprocket parameters were mixed-up. Optimized code so it could render faster.