EPUB import authors, metadata pb_section_author

quick fix to bring in author information from EPUB metadata. Change in this commit to highlight is that it's now grabbing both dc:creator and dc:contributor (instead of dc:creator & dc:rights). If author information is all we're after, then dc:contributor is more suitable (if it's populated). Changes still permit more than one dc:creator and more than one dc:contributor — http://www.idpf.org/epub/20/spec/OPF_2.0_latest.htm#Section2.2.2