open: get kTrackerSignature variable from tracker_private.h

Update copyright.

src/bin/open.cpp

@@ -2,7 +2,15 @@
  * Copyright 2003-2007, Axel Dörfler, [email protected].
  * Copyright 2005-2007, François Revol, [email protected].
  * Copyright 2009, Jonas Sundström, [email protected].
- * All rights reserved. Distributed under the terms of the MIT License.
+ * Copyright 2014 Haiku, Inc. All rights reserved.
+ *
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Axel Dörfler, [email protected]
+ *		François Revol, [email protected]
+ *		John Scipione, [email protected]
+ *		Jonas Sundström, [email protected]
  */
 
 /*! Launches an application/document from the shell */
@@ -20,8 +28,7 @@
 #include <String.h>
 #include <Url.h>
 
-
-const char *kTrackerSignature = "application/x-vnd.Be-TRAK";
+#include <tracker_private.h>
 
 
 status_t