Function returns string in ?q1=v1&q2=v2 format
from passed config key-value pairs

@param {Object} config
@returns {undefined}
function(config) {
			if(!config) {
				return "";
			}

			var result = [];

			for(var key in config) {
				if(typeof config[key] == "undefined") {
					continue;
				}

				result.push(key + "=" + config[key]);
			}

			if(result.length > 0) {
				return "?" + result.join("&");
			}

			return "";
		}