* + duckdb support
needs the forked version of [duckdb-engine](https://github.com/alitrack/duckdb_engine)
* Update duckdb.py
update _time_grain_expressions
* removed superfluous get_all_datasource_names def in duckdb engine spec
* added exception handling for duckdb single-threaded RuntimeError
* fixed linter blips and other stylistic cleanup in duckdb.py
* one last round of linter tweaks in test_connection.py for duckdb support
Co-authored-by: Steven Lee <admin@alitrack.com>
Co-authored-by: Richard Whaling <richardwhaling@Richards-MacBook-Pro.local>
