[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.

usr/lib/PY_VERSION/*-packages/cubicweb/entities/
usr/lib/PY_VERSION/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/PY_VERSION/*-packages/cubicweb/*.py