Add syslog support

Currently we don't have any way of exporting an access log. This could be implemented by supporting the syslog standard in rfc3164 and/or rfc5424 format. For the message format of access logs either the nginx or haproxy defaults could be used so it's supported by a wide variety of tools out of the box

未指定任何文件、测试或入口点；先查找访问日志是如何生成和导出的。明确需要 RFC3164、RFC5424，还是两者，并选择 nginx 或 haproxy 的消息格式；完成的标准是能够通过约定的 syslog 格式导出访问日志。

由索引模型根据 Issue 内容生成。