Started to work on king threats

Sources/Engine/utils.swift

@@ -1,4 +1,15 @@
-public enum Color: UInt8 {
+public enum Color: UInt8, CustomStringConvertible {
 	case Black = 0
 	case White = 1
+
+	public var description: String {
+		return switch self {
+		case .Black: "b"
+		case .White: "w"
+		}
+	}
+
+	public static prefix func ! (rhs: Self) -> Self {
+		return rhs == .White ? .Black : .White
+	}
 }