Parametric BLTouch rear sensor mount

This is a remix of https://www.thingiverse.com/thing:2219963 to allow mounting a BLTouch sensor on the rear bearing of an Anet A8. I've included the customizer to allow the height
and many other features to be custom set for any printer . The "Measured Height" parameter is used to calculate the correct height with the 8.3mm offset to the nozzle. You simply need to move the print nozzle so that it touches the bed then measure the distance of top mount screw hole (on the rear lower bearing)