统一返回的状态码

<table> <thead> <tr> <th>code（状态码）</th> <th>message（说明）</th> </tr> </thead> <tbody> <tr> <td>-1</td> <td>系统错误</td> </tr> <tr> <td>0</td> <td>成功</td> </tr> <tr> <td>1</td> <td>失败</td> </tr> <tr> <td>2</td> <td>参数有误</td> </tr> <tr> <td>4</td> <td>没有权限</td> </tr> </tbody> </table>