Always charge when price is lower than normal

[jmalm]

When the anticipated departure time is set to a time point beyond what we have electricity prices for, the scheduling just repeats the current date's price information and uses that to schedule charging. But if the current prices are lower than normal, we might miss an opportunity to charge at low prices, because the scheduler "thinks" it's going to continue like that.

We could compare the current date's prices to, say, the past seven days and also charge on hours that are significantly lower than the average.