card: Add command "ll"

* tools/gpg-card.c (cmd_list): Add optional ar use_opt_cards.
(enum cmdids): Add cmdLISTCARDS.
(cmds): New command "ll".
(interactive_loop): Ditto.

Using "l --cards" is a command required very often thus it makes sense
to have an alias for it. ll also allows to switch the card without
showing the long listing.