[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.