[Feature] Replace default Shapefile with GeoJSON in “GIS File input” and “GIS File output”

This is a minor enhancement, but it is justified by didactic and rational reasons related to a better future for the geospatial domain.

In 'GIS File input' and 'GIS File output', replace 'Shapefile' with 'GeoJSON' as the default file format.

Shapefile is a deprecated file format — see http://switchfromshapefile.org/ for more information.