QUBD oneup / twoup endstops

The endstops are remixed from Macattack's. The changes are to allow clearance for the 25mm aluminium coupler on the z axis screw and allow extra travel to take advantage of the E3D-V6 type extruder. If you use with the standard extruder you will need a longer 3mm screw for the Z endstop pusher. Depending on the type of bearing holder you might also need an extra something on the bearing holder to push the x stop. I used small stick on feet as in the photo. Longer M3 screws to the original will a