Census municipalty's boundary doesn't have 'COD_PROV'

[MaxDragonheart]

I added manually the column 'COD_PROV' and if this column won't be added in the future from ISTAT, I'll add it. The field 'COD_PROV' is present in 1991, 2001, 2011 data.
Check the link sometimes.

[MaxDragonheart]

Activity related to #44 . If the property will be added to ISTAT, don't forget to remove PRO_COM_T to the config.py's row related to 2021.