Per layer lift_dist_mm

[micaelbergeron]

@cbiffle First things first, what a wonderful job you did here.

I'm looking at this specifically because I own a Mars 2 Pro, and it struck me as silly that the lift distance would be the same independently from the layer's surface area. The small the cross-section, the smaller the time for the vacuum to be filled by the resin for the next layer. Without going into fluid dynamics, I think there could be a huge improvement in print speed by making this parameter dynamic per layer.

Now looking at https://github.com/cbiffle/catibo/blob/master/doc/cbddlp-ctb.adoc#the-layer-table it seems like this would be impossible, am I right? There is no way to change this setting after the print has started, and it isn't override-able from the layer datum?