revisiting vtree (CSG tree)

[hrgdavor]

Here is a start of a discussion regarding the previous attempt to generate tree of operations from modeling,

I my mind this would enable different kinds of optimisations and other use-cases not possible with direct execution of modeling functions.

• diff plus redo of only parts that changed (after param change)
• executing on demand certain operations
• referencing vtree by clicking on the model
• referencing source from model or vtree
• evaluating vtree in different preview/export/fidelity modes (fast preview for dev, full execution for export)
• simpler usage of different boolean libraries for different purpose, or using some new faster one

This could allow designing modeling part of jscad to focus on expressing the ideas and separating the parts that actually produce meshes or do boolean out of it.