[server] add a looping task to free unused cnxsets capture by dead pyro When a pyro client disconnects, we're not necessarily notified so they can hang on to their session/cnxset forever. Don't let them do that. The hacky looping task is only installed when pyro is enabled. This optional activation save this very hacky patch from being rejected. closes #2825380

/* sortable tables */

table.listing tr .headerSortUp {
  background-image: url(asc.gif);
}
table.listing tr .headerSortDown {
  background-image: url(desc.gif);
}
table.listing tr .headerSortDown, table.listing tr .headerSortUp {
   background-color: %(listingBorderColor)s;
   background-repeat: no-repeat;
   background-position: center right;
}