Filter spatial outliers

[ezwelty]

Some sources contain locations which, based on their geographic coordinates, are clearly wrong. Examples include:

• Brazil > Rio de Janeiro > Niterói
• United States > New York > Arlington > Vassar College
• Belgium > Vlaams Gewest > Agentschap Wegen en Verkeer
• Canada > Québec > Montréal
• United States > Maine > Bath

These could be filtered out by either:

• Adding an optional bounds to SourceProperties. This has the advantage of directly working with the existing bounds argument of the Source.process method, but is more work to construct.
• Adding an optional radius (or boxWidth) to SourceProperties. This has the advantage of being easier to construct, and could make use of a center determined by geocoding country, state, city, designation. It could be reformulated as a bounds (hence boxWidth) to make use of existing functionality.