Add GPL modules

MediaBrowser.Controller/Entities/TagExtensions.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using MediaBrowser.Model.Extensions;
+
+namespace MediaBrowser.Controller.Entities
+{
+    public static class TagExtensions
+    {
+        public static void AddTag(this BaseItem item, string name)
+        {
+            if (string.IsNullOrWhiteSpace(name))
+            {
+                throw new ArgumentNullException("name");
+            }
+
+            var current = item.Tags;
+
+            if (!current.Contains(name, StringComparer.OrdinalIgnoreCase))
+            {
+                if (current.Length == 0)
+                {
+                    item.Tags = new[] { name };
+                }
+                else
+                {
+                    var list = current.ToArray(current.Length + 1);
+                    list[list.Length - 1] = name;
+
+                    item.Tags = list;
+                }
+            }
+        }
+    }
+}