Check that client is playing the right item

Send date when playback command is emitted
Rename some classes

MediaBrowser.Model/Syncplay/PlaybackRequestType.cs

@@ -0,0 +1,33 @@
+namespace MediaBrowser.Model.Syncplay
+{
+    /// <summary>
+    /// Enum PlaybackRequestType
+    /// </summary>
+    public enum PlaybackRequestType
+    {
+        /// <summary>
+        /// A user is requesting a play command for the group.
+        /// </summary>
+        Play = 0,
+        /// <summary>
+        /// A user is requesting a pause command for the group.
+        /// </summary>
+        Pause = 1,
+        /// <summary>
+        /// A user is requesting a seek command for the group.
+        /// </summary>
+        Seek = 2,
+        /// <summary>
+        /// A user is signaling that playback is buffering.
+        /// </summary>
+        Buffering = 3,
+        /// <summary>
+        /// A user is signaling that playback resumed.
+        /// </summary>
+        BufferingComplete = 4,
+        /// <summary>
+        /// A user is reporting its ping.
+        /// </summary>
+        KeepAlive = 5
+    }
+}