getFetchPack fixes, spread fetch pack requests.
Websocket improvements:
* Log on_close/on_fail/on_open calls.
* Ping out connections.
* Improve ping logic.
* On websocket ping out, close abnormally.
* Avoid deadlock when shutting down websocket endpoint
Add stl module for c++11 compatibility classes
Add Beast.Insight stats collection module
Add CollectorManager for Beast.Insight support