Support install by `bin/plugin`, dealing with config files reallocation

标准的HTTP协议返回的是 ETag，而不是 ETags，代码中已经改为 ETag。

对 use_smart 做详细说明。

It's more readable with markdown format 😎

curl -XPOST http://localhost:9200/index/fulltext/1 -d'
{"content":"美国留给伊拉克的是个烂摊子吗"}
'
======================================
like above.elder seems ok,but can not be searched.