dox fix: updated doc of WallOverlap (CURA-1640)
dox fix: updated doc of WallOverlap (CURA-1640)

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