country_or_continent_by_code

[yakra]

country_or_continent_by_code is kinda fugly. Get rid of it and replace the country & continent containers with unordered_maps.

• [ ] std::pairs should work the same.
• [ ] Unless it's necessary to retain the order within the containers. Do we iterate thru them?
• [ ] How is equivalent stuff done in siteupdate.py? What exactly is done again?