Filter Out Supporting Statistics

[vjkoskela]

The telemetry sink needs to filter out unspecified statisitcs that are only used for supporting data (e.g. for mean don't send sum and count; unless specified). Longer term this filtering likely belongs on the ReMet side if want to be able to recombine data for telemetry. This is a little ways off so I'm confident we'll get good mileage by adding the filter to the telemetry sink.