Yet another customizable bearing

This is actually my yesterday's evening-hack. It's redundant, because there are many bearings in thingiverse and it's of no use because I have loads of proper cheap Chinese metal bearings of different sizes and I guess that you have some, too. I just made ist to distract me from some other project, a heat-exchanger. Anyway, I share it for fun. Maybe someone likes the look of my rounded edges or maybe someone gets some inspiration from the code, like not to work with the basic object directives so much when constructing objects but to increase use of linear_extrude() and rotate_extrude() with parameterized polygons stuck together with concat(). A good practice could be changing the function kreislinie(), that returns the 2D-points of an arc, so that start- and end-angle can be overwritten by start- and end-height,
This is also an experiment to give Error messages and Object-Information to the user via text-output in customizer. Unfortunately newline-characters aren't rendered as such,