Parametric Pulley - Improved

I added some features to droftart's pulley generator to make it more versatile.

There is now support to generate smooth idlers with the same dimensions as the toothed versions (useful for idlers on Core style printers, for example).
I also added support for defining the height and width of the retainer flanges seperately. This allows you to deviate from the standard 45° angle for the flanges to provide more guidance to the belt with less wasted height.
I also cleaned the code up a bit and improved indentation, brace style and layout.

Attached are two .stls for GT2 idlers, designed to fit directly onto 608 bearings.