card: New option --info for command list and select by s/n.

* tools/gpg-card.c (cmd_list): add option --info.  Factor soem code
out to ...
(print_card_list): new.

This change allows to use the printed s/n to sleect another card
instead of using the index. For example:

gpg/card> l --cards
0* D276000124010200FFFE50FF6E060000
1  D2760001240102000005000000370000

Now select the second card but do not print the entire listing, just
the card index, s/n and applications. We also select by s/n:

gpg/card> l --info D2760001240102000005000000370000
1* D2760001240102000005000000370000

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