refextract: improve author/affiliation extraction

• Added extra 'end of author section keyword'. Added a new 'bad unicode' character, and made sure to check for bad characters in both author lines and affiliation lines.

• Improve overall program flow of handling requests to extract authors or affiliations.

• Use both author matching and keyword matching when locating the top section of a document, in both author extraction and affiliation extraction modes. Plus other improvements.

• Enrich keyword kb.

• Extend author name numeration to include brackets.

• Update usage() to include '--affiliations' option.

• Add a comment explaining why a top section would not be found, and remove some redundant spaces between statements.