Fix duplication of queries in sqerl_rec

* The default query definition contained a bug in which the
  fetch_by_FirstField query was specified twice.

* Default and custom query merging was broken. First, the merge was
  happening before the query names were normalized via
  join_atoms. Secondly, keymerge was being used instead of ukeymerge and
  thus duplicates were being kept (though the order was such that the
  desired behavior was achieved in terms of custom queries overriding
  defaults).