Auto-set Stellarium's location on launch

I propose we add a new key to the init_location section of the INI file (use_ip_geolocation_if_available = true | false). If this is set to "true" then, upon launch Stellarium attempts to ping a remote web service to get the approximate location of the computer's wan IP address (http://www.ipinfodb.com/ip_location_api.php). If Stellarium receives a response from this web service with a city then it uses this location as the location, if not, it falls back to what the INI file specifies.