Expose fetchDataSource

[lmeysel]

When working with factories, it would be nice to have the fetchDataSource() to be exposed to be used in factories. This makes sense, as we probably want to use seeders with factories in a dev enviornment as well as for testing. There the datasources may differ. And as we do store them "globally" we could use this mechanism to easily get the right datasource for whatever enviornment the factory is running in.