Show the present state of each device first in the Grafana dashboard

The dashboard started with gauges and histories of equal weight, so a power failure and its effect were hard to find. The first rows now show the charge, the power source, the time remaining, and the errors of each device. Below them, one band shows each period on battery power, and one chart shows the charge of the three devices.

The charge history adds the pack current of the JBD and the River 2 on a right axis, as dashed lines in the color of each device. The charge limits apply to the charge lines only.

A time-remaining panel with no estimate now names the state. The JBD panel shows "On mains" while the pack does not discharge. The River 2 panel shows "Idle" while the device reports 5999 minutes for the two directions.

The River 2 errors panel names the module that reports a code and shows the code in hexadecimal. The solar controller reports 4096 with no solar input, and the panel counts that value as zero.

README.md

@@ -196,8 +196,9 @@ InfluxDB connection details can also be supplied via environment variables (`INF
 Run `python tools/generate_grafana_ups.py` to write `grafana-ups.json`. Import
 that file for a three-column view of Network
 (JBD), Desktop (River 2), and NAS (River 3). Queries use the `network`, `desktop`,
-and `nas` tags, respectively. It uses the same 24-row grid height as the
-original dashboard. Select an InfluxDB data source configured for Flux.
+and `nas` tags, respectively. The top rows show the present state of each
+device, the power source history, and the charge history. Select an InfluxDB
+data source configured for Flux.
 See the [dashboard guide](docs/grafana-ups.md) for setup and measurement limits.
 
 ## Development