refextract: further changes

• Further changes made to refextract. Corrects problems noted by Annette. Including:
  • support for the unicode character 's' with a tilde
  • support for volume numbers separated with a hyphen
  • making sure that the first author in an author group, if starting with an 'A' initial, must have a full-stop after that first initial
  • support for hyphens between initials
  • support for a separated surname 'prefix'
  • looking for bad 'et al' placement (before an author group rather than after), which causes the author group to be ignored
  • arXiv suppression: removing 'arxiv' or 'e-print arxiv' before a report number and after a title
  • ed. ==> eds?.
  • corrected placement of 'et al' and the last 'ed.' pattern (reversed)
  • support for author groups in brackets