This function generates a dataset to be used for indexing
country-year datasets against the validated CoW states membership. In
short, it will permit the user to quickly drop observations from
country/territory-year data that although they are commonly included in a
variety of political/geographical datasets, these nations or territories
may be disputed (Palestine, Kosovo pre 2008), have a parent nation (Puerto
Rico), or have other peculiarities that do not align with international
standards (CoW, G&W, WDI, IMF).
This is built off of the states packages, which matched the official
Correlates of War record at the time of publishing.