Ft-i3 Mega adjustable z stop

Adjustable z end stop. Uses the stock holder with 2 longer m3 bolts, which were in the kit already, and a m4 x 25 with two m4 nuts. I used this https://www.thingiverse.com/thing:1727889 to model from. Also included a surface model for anyone who wants to modify it.

10/18/18 added a longer block - I changed the springs on my bed to 20mm ones.