Enhance nginx ui docker image

[0xJacky]

• fix: log viewer error when using docker [error] /var/log/nginx/access.log #371 .
• fix: close 2.0 beta.17 容器中的 access.log 没有指向 /dev/stdout，这与文档描述不符 #312
• feat: use s6-overlay to manage the services in docker Docker 容器内的多进程建议使用 s6-overlay 管理 #308 .
• feat: use settings env to skip install 修改配置报错runtime error: invalid memory address or nil pointer dereference #357 .
• feat: use env to predefine admin user Add Env to predefine admin user #214 .
• feat: customize local environment name Nginx UI 的默认环境：本地，这个名称能否自己编辑？ #313 .
• feat: use settings file to predefine nodes [Feature] 通过配置文件设置运行节点(Environment) #169 .
• feat: reload cluster node settings from settings file. [Feature] 通过配置文件设置运行节点(Environment) #169
• chore: update documentation about this pr.

[funcfang]

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