feature #392, authentication keys, history log

When a user successfully performs an authentication with an auth_key, Piwigo
registers it in the history table.

For now, it is not shown/searchable in the history screen, but we can add it
in the future and we can provide a plugin with specific details about
authentication keys usage.

include/functions.inc.php

@@ -446,6 +446,7 @@ INSERT INTO '.HISTORY_TABLE.'
     image_id,
     image_type,
     format_id,
+    auth_key_id,
     tag_ids
   )
   VALUES
@@ -459,6 +460,7 @@ INSERT INTO '.HISTORY_TABLE.'
     '.(isset($image_id) ? $image_id : 'NULL').',
     '.(isset($image_type) ? "'".$image_type."'" : 'NULL').',
     '.(isset($format_id) ? $format_id : 'NULL').',
+    '.(isset($page['auth_key_id']) ? $page['auth_key_id'] : 'NULL').',
     '.(isset($tags_string) ? "'".$tags_string."'" : 'NULL').'
   )
 ;';