WebSearch: date after, date before bug fix

* Fixes unit tests;
* Fixes method '_convert_spires_date_after_to_invenio_span_query';
* Fixes method '_convert_spires_date_before_to_invenio_span_query';
* Fixes regexp used by '_convert_all_dates' and th previous two methods;
* Fixes indentation for kwalitee.