Improved Z-probe limit switch holder for Auto Bed Leveling

This is a remix of the Z-probe holder designed by Michael Zenner (zennmaster), thing #167430.
Since not all extruders are created equal, the lever length is adjustable / customizable. Also one can use either M2.5 screws and nuts (hard to find, for me at least) or a small nylon tie to hold the limit switch.
I improved a few other small details (better fit of the servo arm, reinforcement, etc) while sticking to the original design.
OpenSCAD source is included so this part can be further remi