merge r6368,6410 from branch-2.1 to trunk

- merged the linkroot integration with the existing gallery_url (unique $conf['gallery_url'] used for RSS, mail homepage root in the browse path)
- added an option $conf['debug_mail'] - if set all outgoing mails are saved into local_data_dir

git-svn-id: http://piwigo.org/svn/trunk@6411 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/notification_by_mail.php

@@ -381,7 +381,7 @@ function do_action_send_mail_notification($action = 'list_to_send', $check_key_l
                 array
                 (
                   'GOTO_GALLERY_TITLE' => $conf['gallery_title'],
-                  'GOTO_GALLERY_URL' => $conf['gallery_url'],
+                  'GOTO_GALLERY_URL' => get_gallery_home_url(),
                   'SEND_AS_NAME'      => $env_nbm['send_as_name'],
                 )
               );