Added preliminary support for DuckDB with ``Frame.to_duckdb()``, ``Frame.from_duckdb()``, ``Bus.to_duckdb()``, ``Bus.from_duckdb()``, ``Quilt.to_duckdb()``, ``Quilt.from_duckdb()``, ``Batch.to_duckdb()``, ``Batch.from_duckdb()`` and ``Yarn.to_duckdb()``.
Added ``name`` parameter to ``Frame.from_xlsx()``, ``Frame.from_sqlite()``, and ``Frame.from_hdf5()
Optimized routines for column iteration and ``Frame.transpose()``.