Attach queen model to piece attributes...
temporarily, 'queen' is a proxy for the future 'piece' model, and
'piece' is a proxy for the future 'square' model.
Rename queen.js -> piece.js & piece.js -> square.js
Rename Piece & Queen classes to Square & Piece, respectively
Merge branch '23-10-have-square-model-attributes-piece-models-2'