Pawn

Implement the base Pawn class (fyi- pretty different from the Bishop and Rook Class).

> The pawn (♙, ♟) is the most numerous piece in the game of chess and, in most circumstances, the weakest. It historically represents soldiers or infantry, or more particularly, armed peasants or pikemen.[1] Each player begins a game with eight pawns, one on each square of the rank immediately in front of the other pieces. Check out the wikipedia entry [here](https://en.wikipedia.org/wiki/Pawn_(chess)) for more information.

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