Document initialLayersSetup()
Document initialLayersSetup()

Better structured, really.

Contributes to issue CURA-1507.

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