Dump all sample data into a given directory...* scripts/sampledata.py: Import gen_dropdown_json.
(main): Dump all the sample data from all the datasets into a given directory.
Use context manager with database connection...Use the `with` context manager with database connections and cursors
to ensure that they are closed once they are no longer needed.
Where it was not feasible to use the `with` context manager without a
huge refactor/rewrite, the cursors and connections are closed manually.
