[Metadata] Old-style DOIs in citations: make xml-friendly

Crossref deposits fail if old-style DOIs with xml-incompatible tokens are included in the references list. At the moment, these need to be corrected by hand before successfully depositing.

Solution: need to correctly render the DOI's XML predefined entities ", &, ', <, > to their respective &quot;, &amp;, &apos;, &lt;, &gt; representation.

Place to change: in journals/create_citation_list_metadata.html, line 43.