Enhancement: Add counters

[anjohnson]

It would be nice if both the old and new (JSON) log clients could keep a counter of how many puts they have actually logged which get displayed by the Show commands. This would be is helpful for diagnosing issues with connections and access security configuration. Probably should be implemented using an epicsAtomicInt.

[anjohnson]

Another useful counter would be to count how many puts are being filtered out by the burst filter, so we can tell whether it was 1 or 1000 puts that we didn't see.