LPS-37746 Export DDL Data Definitions and DM Document Types independently

Hi Máté,

I've added the required changes to support exporting DDL Data Definitions and DM Document Types independently. This way, even if there aren't any DDL Recordsets / DM File Entries, the Data Definitions / Document Types can be exported. For DM I haven't included Metadata sets, since I'm not sure if they are a dependency of the File Entry or the Document Type, but this could be improved later.

Please, verify my changes and let me know if I've missed anything.

Thanks!