This plugin can perform the standard metric modifications using override semantics.

This functionality currently has race conditions that can result in the
output deadlocking.

* Included system databases in server properties, added backup/restore throughput counter, error counters, and user settable counters.

* Added more resource governor counters.

* Added Target and Total Server Memory counters.

* Removed the c_type tag from the performance counters query, added more documentation instead.