Merge Country and OverseasTerritory location types

These are now just to be called "World locations".

This is to remove any potential political issues over whether a location is a country or not (the FCO can differ from formal definitions).

This involved considerable noise changing all the factory references to remove calls out to country etc. in order to clean up, but the basic code is simple.

https://www.pivotaltracker.com/story/show/46713179