added a field with information about how precise is the geocoded result

Added a field for the google maps and bing provider that contains information about how precise is the geocoded result, the result can be low, medium, or high, depending on how confident is the service that has geocoded the address.
Oh sorry, it is related to the `PRECISION_LEVEL_HIGH`, `PRECISION_LEVEL_MEDIUM` and `PRECISION_LEVEL_LOW` constants. 

You don't use constants in the BingMapsProvider, so i don't think it will be usefull in the GoogleMapsProvider.