- added new package 'compatibility'  that ensures that the code also works with older versions of Python and GDAL
- added __init__.py to package level

geo.raster.reproject:
- warp_ndarray(): some modifications to ensure compatibility

geo.coord_trafo:
- lonlat_to_pixel(): fixed a Python 2.7 incompatibility

io.raster.gdal:
get_GDAL_ds_inmem(): some modifications to ensure compatibility

io.raster.GeoArray:
- fixed some Python 2.7 incompatibilies

io.temp_io: added new module temp_io for managing temporary files

processing.shell:
- subcall_with_output(): added verbose mode

ptds.__init__:
- added validation of GDAL version