Sink overflow and drain cover

A customisable and parametric overflow and drain cover. The scad will produce a drain cover for anything from a hand basin or bath overflow to a floor drain. Even works as a kitchen sink strainer when rinsing in the sink. Remixed from https://www.printables.com/model/85515-bathroom-overfill-cover-parametrizable-openscad by @Bilbo_176424 Added an epsilon to difference() functions to improve the look of the preview Added an option for a customisable number of slots in the tube wall which automatically adds a locking ring on the far end of the tube wall Added customisable parameters for face and bevel element sizes Changed how some calculations were done so elements were more parametric with new changeable parameters Added a customisable parameter for number of ribs in the face Made the cutout in the center hole optional Made the center hole diameter customisable and removable Added customisation parameters to allow sloping of tube walls The .json file has been provided for some examples.