fix wells collection dictionaries

[andrea-bistacchi]

The WellCollection dictionaries were as follows:

    well_entity_dict = {
        "uid": "",
        "Loc ID": "undef",
        "properties_names": [],
        "properties_components": [],
        "properties_types": [],
        "markers": [],
        "vtk_obj": None,
    }

    well_entity_type_dict = {
        "uid": str,
        "Loc ID": str,
        "properties_names": list,
        "properties_components": list,
        "properties_types": list,
        "markers": list,
        "x_section": str,
        # this is the uid of the cross section for "XsVertexSet", "XsPolyLine", and "XsImage", empty for all others
        "vtk_obj": object,
    }

Was "x_section" missing in well_entity_dict for some reason?

I added it. This will allow projecting wells to x sections (a new XsWell class will be needed for this).