Add a time series plot of 'Current Consumption' stat

[radh21301]

In the 'Current Drive View', there is a box showing the current consumption in wh/mi or wh/km. It is a single number. It would be awesome if we can see a plot as that value changes over time, just like the plot on the 'energy' app on Tesla.

[swiffer]

isn't that what's covered by the power graph ? (while beeing a different unit, but we should be able to calculate that based on current power and speed, right?)

[swiffer]

	case
		when avg(speed) < 5 then 0
	  else coalesce(avg(power) * 1000 / nullif(avg(convert_km(speed::numeric, '$length_unit')), 0), 0)
	end as consumption_kwh_$length_unit,

guess adding that one would help, right?