public PkgDownloader(string url)
{
var client = new GregClient(new Greg.AuthProviders.BasicProvider("test", "test"), url);
var req = HeaderCollectionDownload.ByEngine("dynamo");
var response = client.ExecuteAndDeserializeWithContent <List <PackageHeader> >(req);
Console.WriteLine("file downloaded from " + url + req.Path);
Lists = response.content;
}