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.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>