Report stats on accounts with and without code

[seanyoung]

Signed-off-by: Sean Young sean.young@monax.io

[silasdavis]

Perfect just minor remark on IterableReader

[silasdavis]

We sure we want to pile this on IterableReader?

[compleatang]

Can't add a comment on the line but we need to add the appropriate metrics into func AddMetrics() with something like:

burrowMetrics["Contracts"] = prometheus.NewDesc(
	prometheus.BuildFQName("burrow", "accounts", "contracts"),
	"Current contracts on the chain",
	[]string{"chain_id", "moniker"}, nil,
)
burrowMetrics["Users"] = prometheus.NewDesc(
	prometheus.BuildFQName("burrow", "accounts", "users"),
	"Current users on the chain",
	[]string{"chain_id", "moniker"}, nil,
)

and also something in func (e *Exporter) Collect(ch chan<- prometheus.Metric) that looks like this:

ch <- prometheus.MustNewConstMetric(
	e.burrowMetrics["Contracts"],
	prometheus.GaugeValue,
	e.datum.AccountsWithCode,
	e.chainID,
	e.validatorMoniker,
)
ch <- prometheus.MustNewConstMetric(
	e.burrowMetrics["Users"],
	prometheus.GaugeValue,
	e.datum.AccountsWithoutCode,
	e.chainID,
	e.validatorMoniker,
)