Remove unwanted spacing before 2nd level list

To remove the unwanted space before the 2nd level list, an non-interfaced
setting needs to be changed.

There might be a better, higher-level way to get the same visual output, but I
am not aware of it.
Set 2nd level itemize marker

Again, this is a matter of personal prefernece. I use MetaPost to draw a
triangle as a second level itemize marker