Custom standing paint modular paint stack shelves

This allows for the creation of custom shelves that work with standing paints and the Modular Paint Stack (MPS). If you're not sure what the MPS is, see the Modular Paint Stack core components. To use this, set the following values: shelf_gridfinity_unit_width - How many Gridfinity units wide the interior of the shelf should be (brackets are added extra). Gridfinity units are 42mm, so 5 would be 5*42 (210mm) plus the brackets on the sides. cylinder_height - How tall the support should be. Typically this is the height of the cap (if there is one at the base) or however many millimeters until the bottle/tube is supported without blocking the label. cylinder_diameter - Diameter of the base of the bottle/tube. Must be <42mm. cylinder_count - How many cutouts to make for paints. Typically this matches the Gridfinity units unless the paints are very small. top_inset - Set to true to angle in the shape that supports the paints on the side. False keeps it straight. See https://github.com/IanGC