add installation without gui & pass arguments to gui

ModpackUpdater.Model/ModpackConfig.cs

@@ -8,7 +8,7 @@ public class ModpackConfig
     public string UpdateUrl { get; set; }
     public string InstallUrl { get; set; }
 
-    public static object LoadFromUrl(string url)
+    public static ModpackConfig LoadFromUrl(string url)
     {
         string result = new HttpClient().GetStringAsync(url).Result;
         return JsonConvert.DeserializeObject<ModpackConfig>(result);