Support common_name and official_name fallback to name

[Jamie-]

I was having similar issues to the reporter in issue #30, however I think it's more useful to instead have common_name and official_name fallback to name.

For example in my use case I want a list of all the common names of all countries, given they don't all have common_name I need to fallback to something else and name seems the most fitting.

Added new unittests for my changed code and all originally passing unittests are passing, some were broken before I started, see #133. All pre-commit tasks are passing.