Update documentation of sendLayerData
Update documentation of sendLayerData

Contributes to issue CURA-1210.

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