VideoLookupInfo: Fix Coverity IDs 700896,700897 Uninitialized scalar fields

In DTC::ArtworkItem::ArtworkItem(): A couple of scalar fields are not
initialized by the constructor.

In DTC::VideoLookup::VideoLookup(): Several scalar fields are not initialized
by the constructor.

Also add several fields to DTC::VideoLookup::Copy() which are missing and I
assume is an oversight.