card: Print the used algorithm of all keys.

* tools/card-call-scd.c (scd_readkey): New.
* tools/card-tool-misc.c (pubkey_algo_string): New.
* tools/gpg-card-tool.c (list_one_kinfo): Print the algo.

It is convenient to see the actual algorithm of keys even if no
certificate has yet been created.

• Signed-off-by: Werner Koch <wk@gnupg.org>