make nicer jigs for aligning rails

[astrobunny]

Make some STLs based on the Y-jig for all X, Y and Z rails, for the 180mm Micron.

Started because the original z-jig was difficult to use properly, had to have a straight block behind or the extrusion already there to use it. Instead I just modelled it on the Y-rail style, and added a cutout so it can still be dual-use like the current one, but touches more extrusion, so has less play and gives a more confident alignment.

This is the z-jig in action:

The original Y-rail jig was too long for the 180mm one, so if you put them both on the ends of the extrusion the area was too short and the rail could not be centered using the jigs.

The original X-rail jig only centered the rail vertically, and you had to manually center the x somehow.

This adds Y-rail and X-rail jigs that give you both the correct centering for them vertically and horizontally.