added a notifications service

MediaBrowser.Model/Notifications/Notification.cs

@@ -0,0 +1,33 @@
+using System;
+
+namespace MediaBrowser.Model.Notifications
+{
+    public class Notification
+    {
+        public Guid Id { get; set; }
+
+        public Guid UserId { get; set; }
+
+        public DateTime Date { get; set; }
+
+        public bool IsRead { get; set; }
+
+        public string Name { get; set; }
+
+        public string Description { get; set; }
+
+        public string Url { get; set; }
+
+        public string Category { get; set; }
+
+        public string RelatedId { get; set; }
+        
+        public NotificationLevel Level { get; set; }
+
+        public Notification()
+        {
+            Id = Guid.NewGuid();
+            Date = DateTime.UtcNow;
+        }
+    }
+}