Kiri Moto stepdown issue fixed

See full issue thread here: https://github.com/GridSpace/grid-apps/issues/52

Some users of Kiri:Moto and CAMLab may have noticed that if you try to mill details that are shallower than the specified stepdown does not generate code to mill those details.

What should be happening is that shallow details should be milled at a smaller step down, and features that are deeper than the specified step down should be milled with several passes at either the step down or less.

Since this was not working properly, users would need to either 1) use a step down that was smaller than any feature, or 2) generate separate gcode files with different specified step downs.

Obviously, doing that is a lot of work and inefficient.

Kiri:Moto users should find that the fix is working. We will push the fix onto CAMLab as soon as we can.