A script to check for unclosed country-level boundaries in MapIt Global

This script does a simple check for missing country-level boundaries:
it gets the coordinates of capital cities of the world from dbpedia
and checks whether there is an O02 boundary in MapIt Global that
contains each of those points.
Add a note in settings.py about Cache-Control for JSON responses

This is to help people (e.g. me) who might might be confused
that there's still a 28 day expiry on JSON results even if
settings.CACHE_MIDDLEWARE_SECONDS is 0.