Calculate z height for each slice depending on slicing mode, some cleanup
Calculate z height for each slice depending on slicing mode, some cleanup

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