allow methods to be disabled and redirected via config

allow methods to be disabled and redirected via config

To prevent accidents like adding http-sources while using tor+http it
can make sense to allow disabling methods. It might even make sense to
allow "redirections" and adding "symlinked" methods via configuration.
This could e.g. allow using different options for certain sources by
adding and configuring a "virtual" new method which picks up the config
based on the name it was called with like e.g. http does if called as
tor+http.