Use methods for different data types #318
Description
As described in issue #316 and the Eurostat API guidelines (https://ec.europa.eu/eurostat/web/user-guides/data-browser/api-data-access) there are different data types that can be downloaded. Currently different data sources branch into different functions based on if-else statements. One possibility for handling multiple data sources and data formats would be to use generic functions for all data types and use object oriented programming, S3 or S4 methods, to determine which method to run for which type of data.
This might potentially make the package more robust and easier to maintain. It would also present a good opportunity to sift through the legacy code.