Dependency overview flags: --of-any and --of-none

Rationale: in a system management situation, have a quick overview of
what's been pulled in as a dependency and what is a potential candidate
for removal.

--of-any:  lists all formulae that are a dependency of any formula*.
--of-none: lists all formulae that are not a dependency of any formula*.

*) 'any formula' actually means formulae to which we apply the flags,
e.g --installed or --all.

--of-any respects -n if given, while it makes no sense for --of-none.