Indent nested menus in navcolumn

I posted this to the dev-list, and later found the request that patches get posted here. This duplicates info in my email to the list.

1) It was impossible in the navcolum to tell which were sub-items and
which were top level items, which makes expandable menus seem silly.

2) The expanded/collapsed widget needs to be put at the top of each
list item. For the nested menus it's /very/ important (else it
floats in the middle of the submenus), and it looked
strange when text of non-nested item's wrapped.