made Audio.Artist plural and removed duplicated of artists into the people collection

MediaBrowser.Controller/IServerApplicationPaths.cs

@@ -40,6 +40,12 @@ namespace MediaBrowser.Controller
         /// <value>The genre path.</value>
         string GenrePath { get; }
 
+        /// <summary>
+        /// Gets the artists path.
+        /// </summary>
+        /// <value>The artists path.</value>
+        string ArtistsPath { get; }
+        
         /// <summary>
         /// Gets the path to the Studio directory
         /// </summary>