deposit: doi syntax validator improvements

* Makes the DOI validator stop validation.

* NOTE the name of the validator was changed to DOISyntax validator
  because of convertion to a class.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
search: facets unicode error fix

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>