Fixing some refactoring bugs, first half-decent external metrics attempt.

Fixed:
* `basicMetricLister` wasn't applying the appropriate start time because I had forgotten to set the `lookback`.

There are still a number of issues:
* The `externalPrometheusProvider` is not hooked up to the web application yet, so it doesn't serve requests.
* The namespace and label approach used in `external_info_map.go` is horrifically incorrect. It doesn't appropriately store multiple series with the same name but different labels.
* The configuration is still not updated to appropriately handle external metrics, it's sort of half-piggy-backing on the pre-existing work.

pkg/custom-provider/metric-converter/sample_converter.go

@@ -0,0 +1,52 @@
+package provider
+
+import (
+	"github.com/prometheus/common/model"
+	"k8s.io/apimachinery/pkg/api/resource"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/metrics/pkg/apis/external_metrics"
+)
+
+type sampleConverter struct {
+}
+
+//SampleConverter is capable of translating Prometheus Sample objects
+//into ExternamMetricValue objects.
+type SampleConverter interface {
+	Convert(sample *model.Sample) (*external_metrics.ExternalMetricValue, error)
+}
+
+//NewSampleConverter creates a SampleConverter capable of translating Prometheus Sample objects
+//into ExternamMetricValue objects.
+func NewSampleConverter() SampleConverter {
+	return &sampleConverter{}
+}
+
+func (c *sampleConverter) Convert(sample *model.Sample) (*external_metrics.ExternalMetricValue, error) {
+	labels := c.convertLabels(sample.Metric)
+
+	singleMetric := external_metrics.ExternalMetricValue{
+		MetricName: string(sample.Metric[model.LabelName("__name__")]),
+		Timestamp: metav1.Time{
+			sample.Timestamp.Time(),
+		},
+		//TODO: I'm not so sure about this type/conversions.
+		//This can't possibly be the right way to convert this.
+		//Also, does K8S only deal win integer metrics?
+		Value:        *resource.NewQuantity(int64(float64(sample.Value)), resource.DecimalSI),
+		MetricLabels: labels,
+	}
+
+	//TODO: Actual errors?
+	return &singleMetric, nil
+}
+
+func (c *sampleConverter) convertLabels(inLabels model.Metric) map[string]string {
+	numLabels := len(inLabels)
+	outLabels := make(map[string]string, numLabels)
+	for labelName, labelVal := range inLabels {
+		outLabels[string(labelName)] = string(labelVal)
+	}
+
+	return outLabels
+}