shadow: create utility sub-menu

Signed-off-by: Ted Hess <thess@kitschensync.net>

@sbyx - I've been thinking about condensing some of the clutter in the config menus by making some selected packages which provide multiple sub-packages not all appear in the main menu list. Here's an example of what I've been experimenting with. Shadow-utils is the main entry and each individual utility are in a sub-menu. The option to select 'all' is included so the previous behavior is maintained.

Let me know what you think. If you hate it, just delete this PR. If all is good, I will do some others.