Trims author fields and remove extraneous ponctuation

Nature adds a semicolon followed by a non breakable space at the end of the
citation_authors template in the News section of the site.

e.g. <meta name="citation_authors" content="Cressey, Daniel; "/>

These characters are now trimmed from the author field for {{Article}}.

Side edits: fixing whitespace issues and improving code documentation.

Future edits: it could be interesting to move this citation handling code in
a more generic helper class to allow more specialized article templates.

Fixes T138