Web search suggestion is loaded async

1. suggestion is async
2. if ping time of domain less than 300ms, then suggestion is still sync
3. #578 #539

Wox/App.xaml.cs

@@ -46,7 +46,6 @@ namespace Wox
                 API = new PublicAPIInstance(mainVM, mainVM._settings);
                 PluginManager.InitializePlugins(API, pluginsSettings);
 
-
                 Window = new MainWindow(mainVM._settings, mainVM);
                 NotifyIconManager notifyIconManager = new NotifyIconManager(API);
                 CommandArgsFactory.Execute(e.Args.ToList());