Allow for collective author types

[paulalbert1]

The last author of this publication is a name of a collective as opposed to an individual.
https://www.ncbi.nlm.nih.gov/pubmed/31031568

                  <Author ValidYN="Y">
                    <LastName>Woods</LastName>
                    <ForeName>N</ForeName>
                    <Initials>N</Initials>
                    <AffiliationInfo>
                        <Affiliation>183University of Wisconsin-Madison, Madison, WI USA.</Affiliation>
                        <Identifier Source="ISNI">0000 0001 2167 3675</Identifier>
                        <Identifier Source="GRID">grid.14003.36</Identifier>
                    </AffiliationInfo>
                </Author>
                <Author ValidYN="Y">
                    <CollectiveName>CMS Collaboration</CollectiveName>
                </Author>
            </AuthorList>

Another example:

Title: Mortality After Pediatric Arterial Ischemic Stroke.
http://asms.cc.weill.cornell.edu/publication/faculty/10004962
https://www.ncbi.nlm.nih.gov/pubmed/29695585