Simplify logic.

Simplify recursive_autoremove by reusing remove_from_rdeps function.
Print unresolved dependencies during install.

While performing install or upgrade job it is generally a good idea
to inform user about dependencies of a package that cannot be resolved
(e.g. they are missing in a repository). However, we should also
think about possibility of package installation even with missed deps.
From my sense, -f flag is not permissive enough to use it for this
purpose.