unify switch/keep/pick/swap keywords

We'll direct them all to pick_cards and dispatch based on the situation
move pass_out_characters_and_coins to after shuffle

I need to give the first player  only 1 dcoin in a 2p game, so we need
to do this after the player order is determined for sure
give first player 1 coin in 2p mode

Fixes #6
test: Make sure the players' coin counts are good
add twoplayer to possible settings
do the 3 sets of 5 thing for 2p variant game only
test: Add tests for 2p non-variant game
help: Add help for twoplayer settings
flip_card: Accept command without space