Add basic board representation methods somewhere sensible for re-use by Players and Game flow

[munichpavel]

The check for win of #17, as well as getting waiting area information for #26 require GameState representation information, like a dict of player piece counts in the waiting and home areas. I have been thinking about where such methods belong. Initially I thought in a Player subclass, since part of the remit of the Player classes is to have different game state representations depending on their "choose move" algorithms.

I didn't want to put it in GameState as I already have the get_board_space method for accessing the game state. But I think GameState is the best place to put some basic, re-usable representation methods like waiting_areas_to_dict(), main_spaces_to_list() and home_areas_to_dict().