Add total_results attribute to result of arxiv_search
test-search: include test of weird results when id_list not found

 - if id_list is syntactically correct but not found,
   result could be single row with empty fields, or (if id has a version
   number), single row with id, link_abstract, and link_pdf
Make the total_result attribute an integer

 - Also, add a test
arxiv_search: split out the search-in-batches as separate function