provide with extended statistics via monitor port

[shindo]

Currently, thevoid provides user with relatively poor and unclear statistics:

$ echo i | nc.traditional 127.0.0.1 20001
{
    "connections": 42,
    "active-connections": 37,
    "application": {}
}

Here, "active-connections" value is how many connections are processing requests with handlers, while "connections" is the total number of connection objects alive.

The latter includes currently active connections, connections that are in "Keep-Alive" state waiting for the next request to process, leaked connection objects.

[shindo]

Here we should discuss what statistics we want to collect.

We can take as a baseline nginx and apache statistics:

• http://nginx.org/en/docs/http/ngx_http_stub_status_module.html
• http://httpd.apache.org/docs/2.2/mod/mod_status.html