BibauthorID: error message when merging of profiles fails

* A message is shown when any of the secondary profiles is associated to
  a User.

* A message is shown when any of the secondary profiles is associated to
  a different ORCID than the one of the primary profile.

* A message is shown when any of the secondary profiles is a coauthor
  to the primary profile.

* A message is shown when the non-admin user tries to merge authors with
  claimed papers.

Signed-off-by: Artem Tsikiridis <artem.tsikiridis@cern.ch>
Merge pull request #156 from atsikiridis/merger-fix

BibauthorID: error message when merging of profiles fails