[WIP] Include power plant outages from ENTSOE

[fneum]

What? Include data on historical planned and unplanned outages of generation and production units from ENTSO-E transparency platform:

https://transparency.entsoe.eu/outages/productionAndGeneration

Why? This will help reproducing historical market results and could be indicative of future conventional power plant availability.

How? The steps to do this are:

1. Downloading the raw outages using entsoe-py.
2. Processing them so that data has time stamps as index, power plants as columns and unavailable capacity in MW as values.
3. Matching the time series to powerplantmatching IDs via the powerplants' EIC codes.
4. [TODO] Integrating them as p_max_pu time series into the PyPSA model.

Remarks

• I didn't think too much about step 4, yet. It likely requires better tracking of IDs that get aggregated in clustering and/or optionally preserving individual blocks in the final model.
• This means getting data on EIC column in powerplantmatching becomes more important as well as preserving individual blocks. We will have to see how good the hit rate is.

Any help welcome if someone wants to finish this off!