Add gSSURGO soil database

[MarconiS]

Data overview: soil database with a few dozen tables with soil surveys information. Data format: geodatabase (.gdb) Main source: https://gdg.sc.egov.usda.gov/GDGHome_DirectDownLoad.aspx Data link: https://nrcs.app.box.com/v/soils Description of the data: data is in the folder July2020 gSSURGO by State. This folder contains a pdf (description of the dataset) and one zip file for each US state. Each zip file contains a geodatabase (.gdb) with the polygons and data tables.