Implement generating sanding lines
Implement generating sanding lines

Basic implementation. It's still quite wrong: It goes right over all borders and holes and doesn't seem to include the start points of each line. We'll fix that up later.

Contributes to issue CURA-3903.

ROBO3D/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine,alephobjects/CuraEngine,Ultimaker/CuraEngine,ROBO3D/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine