WIP: reworking zonalstats to fully integrate with OGR/GDAL
WIP: reworking zonalstats to fully integrate with OGR/GDAL

--HG--
branch : zonalstats

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