Split ref_r for meta-papers

To allow users to refer to both individual reports and meta-papers (e.g. OSC) we want to provide full references for original reports

So, where meta-paper = 1, we move ref_r into ref_meta_r and doi_r into doi_meta_r, and generate ref_r to refer to the individual replication report - often without a DOI but "retrieved from URL" - doi_r will usually but not always be blank