WebSearch: datecreated/datemodified field search
WebSearch: datecreated/datemodified field search

* Added special `datecreated' and `datemodified' fields that would
  search for creation/modification dates of records in the bibrec
  table.  (Again, this is a quick fix only, with hardcoded field names
  at places, like the journal index and the rest.)

inveniosoftware/invenio-search,tiborsimko/invenio-records,inveniosoftware/invenio-search,inveniosoftware/invenio-records,tiborsimko/invenio-search,tiborsimko/invenio-search,inveniosoftware/invenio-records,tiborsimko/invenio-records