Add additional parameters for search api

http://wiki.openstreetmap.org/wiki/Nominatim

street=<housenumber> <streetname>
city=<city>
county=<county>
state=<state>
country=<country>
postalcode=<postalcode>
   (experimental) Alternative query string format for structured
requests.
   Structured requests are faster and require less server resources.
   DO NOT COMBINE WITH q=<query> PARAMETER.