Change electricity price source and improvements

Changed electricity price sourcec fron Nordpool API endpoint to Entso-e API as the Nordpool API is no longer available. Entso-e API requires registration and API-key. Updated parsing the response data.
To update tests real data was fetched and added to the project for the same time period that the previoustests were using. By chance, one date (2023-02-17) in the original time period was missing price data in the entso-e response which led to adding missing data handling.
Added error handling for situations where price data is missing in the api response. Warning about missing data is added to the output.
Some refactoring, moving and renaming implementations

M4R774 / bobweb2