Handling of special (non-geo) phone numbers

[francoisfreitag]

#603 (comment)

In the split phone number field, the list of regions come from phonenumbers.COUNTRY_CODE_TO_REGION_CODE. However, that dict contains a special region with code "001", corresponding to prefixes in phonenumbers.COUNTRY_CODES_FOR_NON_GEO_REGIONS. These prefixes ought to be handled separately (either not proposed or offered individually). Currently, only the last one (+979) shows up, with the label “world”.