Dynamically calculate target_energy

[JanPetterMG]

Thanks for this great addon.

One of my automations failed a few days ago, and I ended up using way more power at the cheapest hour than intended.
My target was 2 kWh, but I ended up using 2.6, and 1.9 the next day. Now I have to stay under 1.5 kWh the next 25 days...

I've set target_energy: 1.5 and it calculates sensor.available_power_this_hour correctly, but it still says 2 kWh as target level in the sensor attributes.

• New attribute specifying target_energy. Editing the YAML doesn't change the target until next reboot
• Take sensor.average_peak_hour_energy into account when calculating sensor.available_power_this_hour.