introduce combind and retraction polygon types
introduce combind and retraction polygon types

senttech/Cura,totalretribution/Cura,ad1217/Cura,Curahelper/Cura,Curahelper/Cura,fieldOfView/Cura,bq/Ultimaker-Cura,senttech/Cura,ynotstartups/Wanhao,fieldOfView/Cura,hmflash/Cura,totalretribution/Cura,fxtentacle/Cura,hmflash/Cura,markwal/Cura,ynotstartups/Wanhao,ad1217/Cura,fxtentacle/Cura,markwal/Cura,bq/Ultimaker-Cura