Support removal of cards

[grifferz]

At the moment it is not possible to remove a card from a pack file while there are games in progress.

If you did then every card after the one you removed would get shifted down by one in people's hands, and there would most likely be an exception as soon as the bot tried to deal the card with the maximum index number to someone.

Once removal of cards is handled, pull request #162 should be merged.