i3 rework hall based auto bed levelling probe

Automaticly retracts, based on the design from MarcoAntonini and adapted for prusa i3 rework extruder and mount.
No extra width for the X-carriage, and no servo needed.
I found it to be more consistent then the servo mounted mechanical switch that I previously used.

Parts needed:

• This printed part
• A hall-0 probe (the arrow shaped one, I got mine from mauk.cc
• A probe (I used a long nail with the head grinded off)
• 2x 5x5x5 magnet
  https://www.youtube.com/watch?v=Pw-_rV1bQAU
  https://www.youtube.com/watch?v=LtXKFc6Ru7o