BibField: backported improvements from pu

* Major update of BibField module with some speed improvements and
  enhancements from pu branch.

* New functional test to verify that the speed of recjson is below two
  times of that of recstruct.  (closes #1687)

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
intbitset: initialization from iterator

* Fixes initialization from an iterator, by peeking
  for the iterator protocol signature in the object
  used to initialize an intbitset data structure thus
  avoiding calling max() in case pre-allocation is
  needed, which would consume the whole iterator
  before allowing the data to be extracted (and
  that would crash when max() is called on an
  empty iterator).
  (closes #1698)

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
OAIHarvest: respect hidden fields

* No longer expose hidden fields via OAI-PMH MARCXML export
  format, following CFG_BIBFORMAT_HIDDEN_TAGS
  configuration.

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
DocExtract: have the daemon extract all added pdfs

Signed-off-by: Alessio Deiana <alessio.deiana@cern.ch>
RefExtract: convert arxiv urls to report numbers
RefExtract: hdl handling