Pass options to `get_passphrase()`.

We now use an `argparser` options instance for get_passphrase
instead of a bunch of single args. This makes the main function
`get_passphrase` less readable (you do not see immediately what
options are really expected), but avoids misleading defaults. We
now use the defaults set in argparser options, i.e. from
`handle_options()` as single source of defaults.