Renames Piece->getColor to Piece->color
Renames several functions

Decided I like shorter function names.

+ Currently, the only thing to get and set on the Board object is a Piece.
Therefore, "getPiece" and "setPiece" are slightly verbose.
+ "position", rather than "getPosition", is plenty sufficient.
+ Following the convention established by "position", "setBoard" is renamed
to "board". "getColor" renamed to "color".