Enable log debug in PHP connector

If you have any problem using filemanager you may want to see what's happening on the server-side.

It's now possible to log actions. To do so, just edit the filemanager.php file and add the following instructions just after creating the Filemanager obejct :

$fm = new Filemanager(); // object creation
$fm->enableLog('/path/to/the/desired/file');

Notice that, by default, logs are located into /tmp/filemanager.log file.