customizable pulley

This is a simple pulley design I made for my own purpose and that I share with you.
Only 3 parameters are needed to customize this pulley :
- wheel diameter : change this parameter to change overall well diameter
- hole diameter : changes center hole diameter for pulley axis
- cable diameter : will change pulley groove and thickness.

Be aware that this Scad doesn't check parameters consistency : you can set hole diameter greater than wheel diameter for example... but it won't be printable.

Two entry points are provided :
- print : generate pulley as a whole part.
- printHalves : generate 2 halves of the pulley to be glued together to avoid overhang when printing.