Revision/revise coord trafo

• Fixed issue of remaining coverage artifacts after running 'make clean-test.
• Revised coord_trafo.py. This fixes an issue that caused pixelToLatLon() to return Lon/Lat instead of Lat/Lon.
• Fixed mapXY2imXY() and imXY2mapXY().
• Added Test_mapXY2imXY(), Test_imXY2mapXY(), Test_pixelToLatLon(), Test_latLonToPixel().
• Removed GDAL dataset input parameters from some functions.
• Revised code style and some docstrings. Added some typehints.
• Bugfix for always raising a RuntimeWarning in fill_holes_within_poly().