Split native collector into it's component parts and make them enablable.

Last login is disabled by default as it's broken on ubuntu 12.04
Interrupts is disabled by default as it's very granular and we'll have total interrupts from /proc/stat

Allow ignoring devices from diskstats, ignore ram and loop devices by default.

Use glog for logging.

collector/attributes.go

@@ -0,0 +1,43 @@
+// +build !noattributes
+
+package collector
+
+import (
+	"github.com/golang/glog"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	attributes = prometheus.NewGauge()
+)
+
+type attributesCollector struct {
+	registry prometheus.Registry
+	config   Config
+}
+
+func init() {
+	Factories["attributes"] = NewAttributesCollector
+}
+
+// Takes a config struct and prometheus registry and returns a new Collector exposing
+// labels from the config.
+func NewAttributesCollector(config Config, registry prometheus.Registry) (Collector, error) {
+	c := attributesCollector{
+		config:   config,
+		registry: registry,
+	}
+	registry.Register(
+		"node_attributes",
+		"node_exporter attributes",
+		prometheus.NilLabels,
+		attributes,
+	)
+	return &c, nil
+}
+
+func (c *attributesCollector) Update() (updates int, err error) {
+	glog.V(1).Info("Set node_attributes{%v}: 1", c.config.Attributes)
+	attributes.Set(c.config.Attributes, 1)
+	return updates, err
+}