说明：  AES加密解密，的一个类，按照AES标准算法写的，做了小小优化。希望对学习AES的同学有用处，文件做了详细的注释说明。
(AES encryption and decryption, in a category, in accordance with standard AES algorithm written, and done a little optimization. AES hope to the students learn useful, document a detailed explanatory notes.)