BibAuthorID: reassign signature when rejecting

* Rejected signatures are reassigned to an
  existing profile with the same matchable name.

* If there is no such profile, a new profile is created.

* Claimed signatures not moved when rejecting papers.
  This regression was casusing moved signatures to appear twice
  in the target profile.

* Introduces upgrade script removing duplicate signatures.
  (PR inspirehep/invenio#121)

Signed-off-by: Artem Tsikiridis <artem.tsikiridis@cern.ch>
Reviewed-by: Gilles Louppe <g.louppe@gmail.com>
Acked-by: Samuele Kaplun <samuele.kaplun@cern.ch>