automatic locations

Creates a command that generates locations object for locations with many entries. 
* Neighbor class takes an object with coordinates. Finds other objects with nearby coordinates.
* WebFinder finds uses the Neighbor class to find groups of entries (or any object with coordinates) that  are close to each other.
* CoordinateCenter finds the average latitude and longitude in those groups.
* Csv maker formats a file of world cities.
* LocationFinder takes the coordinate centers and the list of cities.  It finds cities that are near those centers.
* LocationBuilder builds new Active Record Locations for each city that Location Finder finds.
That's up to you. It's fine if you want to make that conversion, I just worry that it's unclear that `@collection` started out as one thing (IDs) then turned into something else (Objects).