Integrate price in plots for "variable" pricing

[j-brendel]

If balanced_market was used as strategy please add the price used for optimization into the figures report->extended_plots-> ..._power_overview. Use a second y-Axis to represent price.

The price that is shown should be the same as in report->gcs->ts.csv-> price [EUR/kWh]

Also, please give in unit ct/kWh both in plot and ts.csv

As a second y-Axis is already used if stationary storage is used, this would mean a third y-axis in this case. Is this possible?

[j-brendel]

To clarify: Calculations already coherent, if prices in price_timeseries_extended.csv are given in ct/kWh. Only column name in ts.csv to be changed from to "price [EUR/kWh]" -> "price [ct/kWh]" And also in plot run_overview_example: "Price in €/kWh" -> "Price in ct/kWh"