Use a geocoder service to convert OreStar addresses to coordinates

[DingoEatingFuzz]

In order to do aggregate queries and visualizations, we need to convert addresses (what OreStar wants for bookkeeping) to lat,lon coordinates (what every gis tool operates on).

Open Elections is already using a geocoder and this should follow what they are doing.

Note: It's possible for campaigns to have multiple associated addresses. Make sure that the address that is used for geocoding is the one that is in the geography associated with the campaign (e.g., if the candidate is running for a multinomah county position, then the address shouldn't be a potential work address in Salem).