Moved logout function in dedicated file

lib/js/logout.js

@@ -0,0 +1,3 @@
+function logout ( ) {
+    window.location.href = script_name+"/logout";
+}

lib/js/manage.js

@@ -39,6 +39,3 @@ function urlinsert() {
     data.append('url', url);
     xhr.send( data );
 }
-function logout ( ) {
-    window.location.href = script_name+"/logout";
-}