Smart Bearing Block remix

Use the original for printing and assembly instructions. This has only a few minor experimental changes. The washers are all replaced with shoulders on the models, and a flex area is used instead of springs. This reduces tolerance though, so they need to fit almost perfect, and probably won't without some tweaking. They're quieter than linear bearings or even the IGUS bushings with the right bearings, and horrible with cheap ones.

N.b. As per discussion, the rods are bent due to the holdowns,