Add Kosovo as a country

[ialja]

It's a bit tricky though, see: SmileyChris/django-countries#5

[ialja]

#322 set the stage, but some more work is needed because Google Maps doesn't return Kosovo as a country when dropping pins over the map. The plan is to have all non supported countries fall back to an "Other" option, so the admin can check the event, assign it to Kosovo, or start a request for a new country.