earthobservations/wetterdienst: Establish black codestyle, fix type casting, add tidy data option

Abstract

establish code style black setup nox session that can be used to run black via nox -s black for one of the supported Python versions add option for data collection to tidy the DataFrame (properly reshape) with the "tidy_data" keyword and set it to be used as default fix integer type casting for cases with nans in the column/series fix humanizing of column names for tidy dat