Use self.null instead of self.blank from model definition to decide if a custom field is required
Remove debug prints
Add part of cross-validation; fix exclude field in inlines; fix pep8
Update admin.py
Rename World to Worldwide
Exclude North America and Anctartica from min_set_countries
Rename World to Worldwide also in the command populating the DB
Copy also the header of the input csv into the output csv
Add copyright headers
Fix name capitalization; add copyright headers
Avoid to duplicate the selected countries per region
Load empty regions as pseudo-countries (also including worldwide)
Add a minimal set of countries with 2 countries per region, excluding Anctartica and North America