Optional "exact" match about geobed HOT 1 CLOSED

There will likely be more matching functions to come, but for now an exact city match was added. Still used through Geocode() but that function now accept an optional GeocodeOptions struct with an attribute ExactCity which, if set, will use this new exactMatchCity() function.

This will first gather a slice of GeobedCity where the city name is found in the search string (case insensitive). From there it will choose a best match based on any available state and country abbreviations. If no abbreviations were found to help narrow down potential cities by the same name, the city with the largest population will be taken.

This way, if a query comes in as "New York, USA" then New York, NY is assumed instead of a New York from another state. Quite frequently, locations are implied based on size or popularity.

from geobed.