mappings/Makefile: Veg+.cs-VegBIEN.csv: Join new Veg+-VegCore.to_self.csv (self-join), instead of Veg+-VegCore.csv, to VegCore-VegBIEN.csv, to support two-level chains of mappings in Veg+-VegCore.csv
mappings/Makefile: Veg+.cs-VegBIEN.csv: Join new Veg+-VegCore.to_self.csv (self-join), instead of Veg+-VegCore.csv, to VegCore-VegBIEN.csv, to support two-level chains of mappings in Veg+-VegCore.csv