[web/facet] Use an Exists node in HasRelationFacet The generated RQL now includes an EXISTS clause. For instance, one gets: :: DISTINCT Any WHERE X is CWUser, EXISTS(X in_group A) instead of: :: DISTINCT Any WHERE X is CWUser, X in_group A for a HasRelationFacet with ``rtype = 'in_group'``, which is more appropriate for testing the existence of the relation. Add a test for this facet along the way.

/* 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;
}