Add helper _get_option_name() which finds name of the option for current Command


Command class has a get_command_name() but it returns the class's name, not the name
of the option as declared in setup cmdclass dict.
Pass format keyword arguments directly to write_utf8()

'{' and '}' were escaped in `header` and `footer` strings
Use `_get_option_name()` to insert command-line info in countries.py header

This way, even if option is renamed, comment will be always up-to-date.