e.g. "show stats server.network"
I failed to realize this had already been implemented without the period in the show stats command (as the command help had not been updated).
However, I would prefer the . approach as it will allow specifying multiple stats, easier wildcarding, etc.
This commit also prevents any stat from having a period in its short name.
the 'count' event is internal, historical data can be built it.
Also includes EventHistogram class for building time based,
bucketed history of event occurances.
Make Stat implement IDisposable for subclasses that might need it.
