BibFormat: affiliation improvements
BibFormat: affiliation improvements

* In case 100__v or 700__v are available, but not
  100__u or 700__u fallback on $v.

* Introduces new multiple_affiliations flag in
  bfe_authors.py in order to optionally display
  multiple affiliations in case these are available.

Signed-off-by: Samuele Kaplun <2e218f779e12714c314fad8ebf6b3041daa21337@cern.ch>

inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio