Allow alternatives to Google for geocoding service

[kvlahromei]

Hi, would be great if you could enable different geocoding services. I guess most of the work is done by existing libs, as geocoder, sou you basically need 'just' patching the Google lookups with generic calls.

[banagale]

@kvlahromei I think this is a great idea, and looking at the geocoder library you've pointed out, I can see how they've abstracted requests into specific common address types.

For example, the address properties for Bing's geocoding service.

I'm setting this to 0.3.0 feature, since it should influence the model work for that release. However, adding this more generic geocoding ability to django-address will probably not come until after 0.3.0.

Updated this issue title from "Google indipendend geocoding services".