ANET A8 Z Endstop fine adjustment

I did change two things:
- The Leg has a 2.95 mm hole for 3mm screws which gives more stability, no more drilling or heating needed anymore.
- The Foot is completely redesigned also for 3mm screw and has a big flat bottom and is easy to screw on to the screw and is used for calibration as a turning knob ;-)

Assembly instructions:
- Mount the switch holder to the frame, add the switch
- put a M3x35 or similar through the legs hole
- add the foot to the screw, tighten it a little bit, no