Allow sorting by catalogue number

classes/torrentsearch.class.php

     'seeders' => 'seeders',
     'leechers' => 'leechers',
     'snatched' => 'snatched',
+    'cataloguenumber' => 'cataloguenumber',
     'random' => 1);
 
   // Map of sort mode => attribute name for grouped torrent page
     'seeders' => 'sumseeders',
     'leechers' => 'sumleechers',
     'snatched' => 'sumsnatched',
+    'cataloguenumber' => 'cataloguenumber',
     'random' => 1);
 
   // Map of sort mode => aggregate expression required for some grouped sort orders

sections/torrents/browse.php

               <option value="snatched"<?Format::selected('order_by', 'snatched')?>>Snatched</option>
               <option value="seeders"<?Format::selected('order_by', 'seeders')?>>Seeders</option>
               <option value="leechers"<?Format::selected('order_by', 'leechers')?>>Leechers</option>
+              <option value="cataloguenumber"<?Format::selected('order_by', 'cataloguenumber')?>>Catalogue Number</option>
               <option value="random"<?Format::selected('order_by', 'random')?>>Random</option>
             </select>
             <select name="order_way" class="ft_order_way">