Revised geocoding: Now uses us_cities_merged table

This update requres a new loctbl database, which can be found at https://s3-us-west-1.amazonaws.com/fidownloads/loctbl.7z

The us_cities table was missing a small number of cities. To solve this problem, the usloc table was compressed into a new table, usloc_center_approx, which contains all of the cities in usloc, but compressed to have only a single entry per city - one with the latitude and longitude closest to the center of the city. A subset of this table was merged into the us_cities database to fill the gaps, adding roughly 3,000 cities and forming the new table us_cities_merged, which is now used for the geocoding.

Some code refactoring was also performed.