support for logging Clojure data structures

We could specify a structured format and a wire protocol for printing/expanding Clojure data structures in a similar way how cljs-devtools work for ClojureScript.

cljs-devtools could then connect to a backend library via websocket and act as a rich logging console for Clojure projects. With support from [Dirac DevTools](https://github.com/binaryage/dirac) we could turn Chrome's DevTools into a nice REPL + logger for Clojure (not only for ClojureScript).

I personally do most of my work on client-side, so it is unlikely for me to spend time on it at this point. But I would be happy to help someone else who would be interested in implementing it to integrate it (I would do the JavaScript part on front-end).

该 issue 没有指出任何文件、测试或入口点。先查看 cljs-devtools 和 Dirac DevTools，然后定义打印和展开 Clojure 数据结构所需的结构化格式和 websocket 协议；完成的标准是后端能够连接到功能丰富的 Chrome DevTools 日志控制台。

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