* removes the pt of face down cards
Instead of setting the pt of a hidden card to the value only known to
you, it's reset to nothing.
Resetting a card while it's already reset does nothing.
Removing the pt of a card is logged as "player removes the pt of card."
instead of "player sets the pt of card to ." (note the missing value).
* reset unknown cards to nothing instead
* replace cardname with card id for unknown cards
fixes#3543
* prefix #
ba985f97e5