Loads shapefiles of states (Länder: LAN), districts (Kreise, kreisfreie Städte: KRS), and municipalities (Gemeinde: GEM) for a given year. The shapefiles are processed and assigned to the global environment as vg250_lan, vg250_krs, and vg250_gem. This function is useful if you want to use the shapefiles with other R packages to plot your data.