[reledit] Fix reledit icons jumpiness (closes #4106867)
Introduce an "invisible" class (copied verbatim from Bootstrap) that
only sets the "visibility" property. "display: none" is the reason for
the whole jumpiness as it actually detaches the element from the
rendered layout. "visibility: hidden" only makes it transparent while
keeping its original box properties (width, height, etc).
[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.