Add no-EPSG compatibility.

This adds compatibility with projections which have no corresponding EPSG code.

• GeoArray.projection is now always set to a WKT1 string (GDAL conform) no matter if the input WKT has an EPSG code or not.
• Added compatibility of GeoArray.show_map() and GeoArray.show_footprint() with input WKTs that have no EPSG equivalent.

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