Usability improvement to kCurlHelper class

In-Portal has kCurlHelper class to automate process of retrieving data from other API's or websites, like Google Data API or RSS feeds.

All works fine, when queried website has no errors. In case if website sends 500 HTTP response code (error) or there will be a connection timeout to that site, then response from kCurlHelper::Send method will be the same: empty string.

Such result is not sufficient for web sites, where empty string means something special response. In such cases I usually check for last HTTP code to be 200 OK and no connection error has occurred.

In attached patch there is new kCurlHelper::isGoodResponce method for doing all that.