Query specific parameters from dataset

Added

• Enable selecting a parameter precisely from a dataset by passing a tuple like [("precipitation_height", "kl")] or
  [("precipitation_height", "precipitation_more")], or for cli/restapi use "precipitation_height/kl"
• Test of restapi with recent period

Fixed

• Bug when querying an entire DWD dataset for 10_minutes/1_minute resolution without providing start_date/end_date,
  which results in the interval of the request being None
• Get rid of pandas performance warning from DWD Mosmix data