Report JS version in _system

[wohali]

Summary

Would be nice to report which version of JavaScript is available on a given system through a remote UI endpoint.

Desired Behaviour

See a "javascript_version": "68" key-value pair in the output of GET /_node/<whatever>/_system.

Possible Solution

The version is available via couchjs -V in the first line of output.

[nickva]

This is fixed:

{
    "collation_driver": {
        "collation_algorithm_version": "13",
        "library_version": "66.1",
        "name": "libicu"
    },
    "erlang_version": "23.3.1",
    "javascript_engine": {
        "name": "spidermonkey",
        "version": "68"
    }
}

We report JS, erlang and libicu versions