Even more minimal MK7 extruder bearing filament feeder

This is a slightly modified version of whosawhatsis' original minimal version. I didn't have the right spring, and the original one seemed to be set up more for 3mm filament. So I borrowed TopperDEL's idea of using a machine screw to create the necessary compression. So this version does not have the quick change feature, but now only needs the 623 bearing and standard M3 screws.