/// <summary>
 /// Add multiple sources directory the list of sources for this ConfigProvider.
 /// </summary>
 /// <param name="provider"></param>
 /// <param name="sources"></param>
 public static void Add(this IConfigProvider <IConfig> provider, params IConfigSource <IConfig>[] sources)
 {
     foreach (var source in sources)
     {
         provider.Add(source);
     }
 }