4.4.2

Service release, bringing fixes.

- Addressing some keyholer limitations seen originally for nested donuts.
 - This was a fairly tricky problem to solve, with multiple parts.
  - The larger 'cutter' was being included in the cut for inner parts, which obviously cut them away.
   - Now, we check for 'lost' area with the keyholer; in case of a change of exposed area, we know geometry has been lost and check for full coverage of outers. Those cutters will be dropped for the re-scan, allowing for continued subtractive processing of the outers.
  - As part of this rescan, some internal duplication of geometry is possible; this is now caught with a clean-up stage to avoid another cause of missed geometry.
   - This fail case was seen with ILB using the ouput from the nested donut scenario.
 - Added keyhole width property to geoCore layer, to make the keyholes larger than the internal default, avoiding loss in sliver/gap sequences.
- GeoCore copy/paste fix.
- NET 6.0 migration.
- Fixed missing progress bar.
- DOE tile preview in layer now also crops 'drawn' to show just tile contents.
- GTK fix for UI scrollable from Eto.Forms project.
- Multithreading work.