Check that client is playing the right item

Send date when playback command is emitted
Rename some classes

MediaBrowser.Model/Syncplay/SendCommand.cs

@@ -0,0 +1,38 @@
+namespace MediaBrowser.Model.Syncplay
+{
+    /// <summary>
+    /// Class SendCommand.
+    /// </summary>
+    public class SendCommand
+    {
+        /// <summary>
+        /// Gets or sets the group identifier.
+        /// </summary>
+        /// <value>The group identifier.</value>
+        public string GroupId { get; set; }
+
+        /// <summary>
+        /// Gets or sets the UTC time when to execute the command.
+        /// </summary>
+        /// <value>The UTC time when to execute the command.</value>
+        public string When { get; set; }
+
+        /// <summary>
+        /// Gets or sets the position ticks.
+        /// </summary>
+        /// <value>The position ticks.</value>
+        public long? PositionTicks { get; set; }
+
+        /// <summary>
+        /// Gets or sets the command.
+        /// </summary>
+        /// <value>The command.</value>
+        public SendCommandType Command { get; set; }
+
+        /// <summary>
+        /// Gets or sets the UTC time when this command has been emitted.
+        /// </summary>
+        /// <value>The UTC time when this command has been emitted.</value>
+        public string EmittedAt { get; set; }
+    }
+}