Groove Bearing Generator

There is a generic bearing generator that is useful if all you want is to print are stand-alone bearings and I used to to define a handful of standard bearings to test it. However, I prefer to include the races directly in my 3D prints so I tend to call the DeepGrooveRaceWay (as a tool to create the races) and DeepGrooveCage separately. I added some smarts to DeepGrooveCage to compute a default number of balls if you like but you can always override this if you like.