Add basic online API support.

osu.Game/Online/Chat/Message.cs

@@ -0,0 +1,34 @@
+//Copyright (c) 2007-2016 ppy Pty Ltd <contact@ppy.sh>.
+//Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using Newtonsoft.Json;
+
+namespace osu.Game.Online.Chat
+{
+    public class Message
+    {
+        [JsonProperty(@"message_id")]
+        public long Id;
+
+        [JsonProperty(@"user_id")]
+        public string UserId;
+
+        [JsonProperty(@"channel_id")]
+        public string ChannelId;
+
+        [JsonProperty(@"timestamp")]
+        public DateTime Timestamp;
+
+        [JsonProperty(@"content")]
+        internal string Content;
+
+        [JsonProperty(@"sender")]
+        internal string User;
+
+        [JsonConstructor]
+        public Message()
+        {
+        }
+    }
+}