refactor(tsdb): changed tsdb time series model to use null.Float instead of pointers

pkg/tsdb/graphite/graphite.go

@@ -80,6 +80,7 @@ func (e *GraphiteExecutor) Execute(queries tsdb.QuerySlice, context *tsdb.QueryC
 
 	result.QueryResults = make(map[string]*tsdb.QueryResult)
 	queryRes := &tsdb.QueryResult{}
+
 	for _, series := range data {
 		queryRes.Series = append(queryRes.Series, &tsdb.TimeSeries{
 			Name:   series.Target,

pkg/tsdb/graphite/types.go

@@ -1,6 +1,8 @@
 package graphite
 
+import "github.com/grafana/grafana/pkg/tsdb"
+
 type TargetResponseDTO struct {
-	Target     string        `json:"target"`
-	DataPoints [][2]*float64 `json:"datapoints"`
+	Target     string                `json:"target"`
+	DataPoints tsdb.TimeSeriesPoints `json:"datapoints"`
 }