3.1 - major update (27-08-2023)

[Zofz]

New features:

1. ODB++
2. Drill/route layer drawings (of cut-outs) are converted into objects (e.g., obround->track)
3. Compare PCB revisions, color-coded differences
4. Hole List,
   • ordered as a tree list, by type, by diameter, by position, by layer
   • provides object count for each category
   • browsing the list and selecting holes by mouse (on the PCB)
   • annular ring and clearance for each layer
5. Old (and considered to be vulnerable) DX9 is now replaced with DX11
6. Bug fixing: flattening, and triangulation, UI... (some still pending)