Wetterdienst

Feature
- CLI: Obtain "--tidy" argument from command line
- Extend MOSMIX support to equal the API of observations
- DWDObservationSites now filters for those stations which have a file on the server
- DWDObservationData now also takes an individual parameter independent of the pre-configured DWD datasets by using DWDObservationParameter or similar names e.g. "precipitation_height"
- Newly introduced coexistence of DWDObservationParameter and DWDObservationParameterSet to address parameter sets as well as individual parameters

Refactor
- Imports are changed to submodule thus now one has to import everything from wetterdienst.dwd
- Renaming of time_resolution to resolution, period_type to period, several other relabels

Refactor
- Large refactoring
- Make period type in DWDObservationData and cli optional
- Activate SQL querying again by using DuckDB 0.2.2.dev254. Thanks, Mytherin!

Fix
- Fix coercion of integers with nans
- Fix problem with storing IntegerArrays in HDF

Feature
- Rename ``DWDStationRequest`` to ``DWDObservationData``
- Add ``DWDObservationSites`` API wrapper to acquire station information
- Move ``discover_climate_observations`` to ``DWDObservationMetadata.discover_parameters``
- Add PDF-based ``DWDObservationMetadata.describe_fields()``
- Upgrade Docker images to Python 3.8.6
- Move intermediate storage of HDF out of data collection
- Fix bug with date filtering for empty/no station data for a given parameter
- Radar data: Add non-RADOLAN data acquisition

Feature
- Add TTL-based persistent caching using dogpile.cache
- Add ``example/radolan.py`` and adjust documentation
- Export dataframe to different data sinks like SQLite, DuckDB, InfluxDB and CrateDB
- Query results with SQL, based on in-memory DuckDB
- Split get_nearby_stations into two functions, get_nearby_stations_by_number and get_nearby_stations_by_distance
- Add MOSMIX client and parser. Thanks, jlewis91!
- Add basic HTTP API

Feature
- Add test for Jupyter notebook
- Add function to discover available climate observations (time resolution, parameter, period type)
- Make the CLI work again and add software tests to prevent future havocs
- Use Sphinx Material theme for documentation

Fix
- Fix typo in enumeration for TimeResolution.MINUTES_10

Feature
- Enhance usage of get_nearby_stations to check for availability
- Output of get_nearby_stations is now a slice of meta_data DataFrame output

Feature
- Add RADOLAN support
- Change module and function naming in accordance with RADOLAN