added a new function polar2polyvert in georef.py which does not use centroids to compute the polygon vertices
added a new function polar2polyvert in georef.py which does not use centroids
to compute the polygon vertices

heistermann/wradlib,wradlib/wradlib,heistermann/wradlib,wradlib/wradlib,kmuehlbauer/wradlib,kmuehlbauer/wradlib