BibConvert: fix arXiv license info
BibHarvest: improved 773 pubnote extraction

* Moves the journal reference (or "pubnote") parsing from XSLT
  to using RefExtract API instead to consolidate on one place
  for all reference analysis.

Reviewed-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
BibTaskUtils: add BibTask sleeping