Emissions chart shows unexpectedly low values

[simonhac]

note that the first bar of the emissions chart is very low:

i suspect this is because we're part way through the 30 minute aggregation period so we're seeing a partial period and we're just summing the emissions in that period, while we're averaging the power readings for power.

(i don't know why the last period is now very low… i suspect we are dropping it.)

proposed solution is to adjust the value so that it is sum(emissions) / count(emissions) * 6 instead of sum(emissions), and use the hatch pattern to show an incomplete period.