Add tests

[philipmat]

Testing the import with every single release may be a bit more difficult due to the long-running nature of the process.
It may be sufficient to test it by periodically adding updated samples.

To that extent:

• create samples of each of the files (1k?)
• call the exporter to convert the files to csv
• compare the number of records extracted
• better: compare against reference csv files to ensure all records have been extracted identically (might not be the best idea since data changes)
• Investigate if we can bring up instances of PG and My and test the importers as well

[philipmat]

tests added and merged to develop