[views] Replace poorly named "invisible" class with "list-unstyled" "li.invisible" actually means "hide bullet". Use a reasonable name instead, such as bootstrap's "list-unstyled" class. This patch also changes the DOM element the class is applied to. "li.invisible" had to be enabled on every "li" tag, whereas the "list-unstyled" class only needs to be applied to the parent "ul" element.

/* 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;
}