Listview CSS: Some rules inadvertently apply to list items of nested listviews

[gabrielschulhof]

In the listview CSS it is assumed that an indirect child li of a listview is the direct child li of that listview, and rules are written with " " instead of ">".

While looking at #6214 I had to circumvent with custom CSS some rules which were being applied to list items of child listviews in a nested listview.