get_records_with_num_cites() now returns intbitset, saving unnecessary list to set to list to hitset conversions.
get_records_with_num_cites() now returns intbitset, saving unnecessary
list to set to list to hitset conversions.

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