embed pb.FetchResponse in metricData type
use the protobuf accessors everywhere

gofmt -w -r '*a.Name -> a.GetName()' *.go
gofmt -w -r '*a.StartTime -> a.GetStartTime()' *.go
gofmt -w -r '*a.StopTime -> a.GetStopTime()' *.go
gofmt -w -r '*a.StepTime -> a.GetStepTime()' *.go