Statsd Plugin

This is interesting: https://github.com/steemit/steem/pull/2447, https://github.com/steemit/steem/issues/2276

> There are two users for the plugin. The developers running the application and the dev/admin wanting to record some subset of data. Some of the user stories that I have come up with.
>
> I am a developer that wants to time the execution of a critical function in steemd and send it to a statsd server so that I can optimize the function.
>
> I am an admin that only wants to record API call counts.
>
> I am an admin that wants to log statsd rather than send messages to a statsd client.
>
> From these stories I have concluded the plugin needs to meets the following requirements:
>
> * Easy to integrate into new and existing code. (Probably Macro based)
>
> * Runtime configurable on output destination (UDP, file, stderr, etc.)
>
> * Runtime configurable on logged statistics.
>
> * Must be low impact and non-blocking.

> Moving ahead with:
> https://github.com/vthiery/cpp-statsd-client

Start by reading the linked Steem pull request and issue, then review the referenced cpp-statsd-client project. Compare the proposed user stories and requirements with the current BitShares codebase; done would require an agreed design for integration, runtime configuration, and non-blocking metric output.

Written by the indexing model from the issue text.