Add Setting for Nominatim Country Code

[northshorenature]

I was wanting the search widget to be able to find US zip codes without appending the ',US' to the end of the search string.

Probably not recommended but I modified line 428 of geo-mashup-geocoders.php
to hardcode 'US' as the countrycodes param :

$geocode_url = 'http://nominatim.openstreetmap.org/search?format=json&polygon=0&addressdetails=1&countrycodes=us&q=' .

It works as desired but will get blown away during the next update.

I started to look at how hard it would be to modify geo-mashup-options.php and OverallPanel.php (and others?) to make a Nominatim Country Code Setting and quickly realized that is beyond my abilities, so submitting as an enhancement request instead.

Thanks so much for the amazing plugin