smallicon for Join notifications

New: White icon with transparent background for Join notifications notification bar icon
Closes #1458

src/NzbDrone.Core/Notifications/Join/JoinProxy.cs

@@ -88,6 +88,7 @@ namespace NzbDrone.Core.Notifications.Join
             request.AddParameter("title", title);
             request.AddParameter("text", message);
             request.AddParameter("icon", "https://cdn.rawgit.com/Sonarr/Sonarr/develop/Logo/256.png"); // Use the Sonarr logo.
+            request.AddParameter("smallicon", "https://cdn.rawgit.com/Sonarr/Sonarr/develop/Logo/96-Outline-White.png"); // 96x96px with outline at 88x88px on a transparent background.
 
             var response = client.ExecuteAndValidate(request);
             var res = Json.Deserialize<JoinResponseModel>(response.Content);