The reader and importer should not only use **kwargs, but update datasource.args with kwargs to find optional settings.
The mapping from datasourcetype to reader and importer should not be hardcoded. Better approach is to have an updateable mapping dict, with API wide `register*` functions to set custom importer and reader.
There are two enhancements:
**kwargs, but updatedatasource.argswithkwargsto find optional settings.dict, with API wide `register*` functions to set custom importer and reader.