[board] Add neighbor and piece modules

Add a Direction enum in the neighbor module
Add Color and PieceShape enums, and a Piece struct to the piece module

board/src/piece.rs

@@ -0,0 +1,34 @@
+// Eryn Wells <eryn@erynwells.me>
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum Color {
+    White,
+    Black,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum PieceShape {
+    Pawn,
+    Knight,
+    Bishop,
+    Rook,
+    Queen,
+    King,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum PiecePlacementError {
+    PieceExistsOnSquare,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub struct Piece {
+    pub color: Color,
+    pub piece: PieceShape,
+}
+
+impl Piece {
+    pub fn new(color: Color, piece: PieceShape) -> Piece {
+        Piece { color, piece }
+    }
+}