Working on the daqd style statistics in cps_recv.

* Linked the admin interface into the dc_stats to allow clearing the crc counters.
* Fixed a bug in the crc logic which would not allow it to always mark a crc (dropped data) on a transition between valid data and no data.
* Added some tests.
* Added a emplace_with_timeout to the message queue to allow implementing the DCStats stop method without blocking forever if a background thread is not running.