Consider improving our set of country names

[mattfullerton]

Notes:
http://publications.europa.eu/mdr/resource/authority/country/html/countries-eng.html
https://github.com/derilinx/ckanext-nrgi-published/blob/master/ckanext/nrgi/schema.json#L771
https://en.wikipedia.org/wiki/ISO_3166-1_alpha-3

cf. #25

[mattfullerton]

@deirdrelee De-milestoning as this issue isn't a clear action item.

In the end the list of countries we display will probably deviate from absolute official country names to avoid having a bunch of countries which start with "the" and so on. A complicated approach where we distinguish labels from values like we have for questions would be possible but I'm not sure its worth it.

So this issue is here just as a reminder that the situation isn't perfect, but probably acceptable.