fix isbn search bug introduced in 3508802, improve query building

- fix: 350880260e filled #searchinput1 instead of #searchinput2
- slightly improved isbn testing
- show error message if user tries to scan HEFTID, since we can't
  lookup those barcodes
- use biblionaut.net instead of labs.biblionaut.net for id lookup
  (faster)
- don't escape search term if it specifies index (e.g. bs.isbn,
  bs.dokid)