Update collection id in xml reader and saver

MediaBrowser.Controller/Providers/BaseItemXmlParser.cs

@@ -571,7 +571,7 @@ namespace MediaBrowser.Controller.Providers
                     }
                     break;
 
-                case "CollectionNumber":
+                case "BelongsToCollection":
                     var tmdbCollection = reader.ReadElementContentAsString();
                     if (!string.IsNullOrWhiteSpace(tmdbCollection))
                     {

MediaBrowser.Providers/Savers/XmlSaverHelpers.cs

@@ -67,7 +67,7 @@ namespace MediaBrowser.Providers.Savers
                     "TVcomId",
                     "RottenTomatoesId",
                     "MusicbrainzId",
-                    "CollectionNumber",
+                    "BelongsToCollection",
                     "Genres",
                     "Genre",
                     "Studios",
@@ -343,7 +343,7 @@ namespace MediaBrowser.Providers.Savers
 
             if (!string.IsNullOrEmpty(tmdbCollection))
             {
-                builder.Append("<CollectionNumber>" + SecurityElement.Escape(tmdbCollection) + "</CollectionNumber>");
+                builder.Append("<BelongsToCollection>" + SecurityElement.Escape(tmdbCollection) + "</BelongsToCollection>");
             }
 
             if (item.Taglines.Count > 0)