Check that client is playing the right item

Send date when playback command is emitted
Rename some classes

MediaBrowser.Model/Syncplay/GroupUpdateType.cs

@@ -0,0 +1,41 @@
+namespace MediaBrowser.Model.Syncplay
+{
+    /// <summary>
+    /// Enum GroupUpdateType
+    /// </summary>
+    public enum GroupUpdateType
+    {
+        /// <summary>
+        /// The user-joined update. Tells members of a group about a new user.
+        /// </summary>
+        UserJoined = 0,
+        /// <summary>
+        /// The user-left update. Tells members of a group that a user left.
+        /// </summary>
+        UserLeft = 1,
+        /// <summary>
+        /// The group-joined update. Tells a user that the group has been joined.
+        /// </summary>
+        GroupJoined = 2,
+        /// <summary>
+        /// The group-left update. Tells a user that the group has been left.
+        /// </summary>
+        GroupLeft = 3,
+        /// <summary>
+        /// The group-wait update. Tells members of the group that a user is buffering.
+        /// </summary>
+        GroupWait = 4,
+        /// <summary>
+        /// The prepare-session update. Tells a user to load some content.
+        /// </summary>
+        PrepareSession = 5,
+        /// <summary>
+        /// The keep-alive update. An update to keep alive the socket.
+        /// </summary>
+        KeepAlive = 6,
+        /// <summary>
+        /// The not-in-group update. Tells a user that no group has been joined.
+        /// </summary>
+        NotInGroup = 7
+    }
+}