move child definitions to db

MediaBrowser.Controller/Persistence/IDisplayPreferencesRepository.cs

@@ -10,6 +10,12 @@ namespace MediaBrowser.Controller.Persistence
     /// </summary>
     public interface IDisplayPreferencesRepository : IRepository
     {
+        /// <summary>
+        /// Opens the connection to the repository
+        /// </summary>
+        /// <returns>Task.</returns>
+        Task Initialize();
+
         /// <summary>
         /// Saves display preferences for an item
         /// </summary>