MAJOR UPDATE: infobot logic overhaul, mediocrebot

infobot.py   - logic more robust, trackCards optional
deck.py      - cardFreq (dict of card frequencies)
dumbbot.py   - delay applies to dumbbot children, -1 means step thru
game.py      - don't discard final cards
gamestate.py - final cards GUI feature (fix end of game discard[-1] GUI error)
humanbot.py  - inherits from infobot, fix targetless GUARD prompt error

Added mediocrebot.py: uses rating system to determine optimal move