option to add package variants before harvesting data

The Dashboard show audit progress also based on existing package variants - eg. if there are multiple package variants, but only the oldest one has been reviewed in Fossology, the Dashboard regards also the newer one as reviewed in the total file count, because in variants only some single files (patches etc.) are usually changed/added, so it's just a matter of a reuse agent that needs to be scheduled in order to have also the new variant fully reviewed.

However, by harvesting only latest project snapshot's data, previous variants are not included, so the total audited file count provided by the Dashboard is not reliable.

To fix this, we need to add all available variants to the session before running "fossy" and "harvest" commands, and properly handle them in the harvest command option that filters packages based on latest snapshot tag (older variants generally belong to a previous snapshot and may be filtered out unless a proper exception is added to the filter)