add utility method that, given a Game, returns the human player
fill in Game.get_location() and the make_move view
Set symbols for human and ai
make get_human_player() into generic _get_player_of_type(), add aliases for get_human_player(), get_ai_player()
remove irrelevant comments from Entity model
record notes on ai decision logic
add Game.next_player() to simply finalizing a turn, add minimal logic to Entity.get_decision() for ai player
add logic to call ai entity's get_decision() method when appropriate, adjust comment formatting, add turn finalization to make_move view