Add *.shp to strandard files

[AlexDo1]

We could add shapefiles (*.shp) to the standard file types. Shapefiles could then always be transformed to *.geojson or *.geopackage files.
I think it would be a good idea to directly parse shapefiles / geospatial data with the json2args packages. I had to convert a .shp file to .geojson for another tool before and it would be nice to be sure that we always expect out geospatial input data in the same format.

First discussed here:

Shapefile.shp is not a good name, as the parameter is then also called Shapefile. Rather use a parameter name that is more descriptive, like: gauges, which would result in gauges.shp.

In addition: @AlexDo1 maybe we add *.shp to the standard file types, but always transform it to *.geojson. or *.geopackage That makes handling geospatial data easier. We can open a discussion for that in the tool-specs

Originally posted by @mmaelicke in VForWaTer/tool_whiteboxgis#10 (comment)

[mmaelicke]

This is obsolete, as the data.extension can limit the data input to literally any kind of data file extensions