Allow calling Zotero.Translate.*.translate without setting translator first.
This simply means that detection code will be run first.
Attempting this with Export translators will fail, because trying to detect a translator does not make sense in this case.
[RecognizePDF] Attempt to search by ISBN even if we found a DOI
(but only if DOI search failed)
Merge pull request #535 from aurimasv/lookup-doi+isbn

[RecognizePDF] Don't skip ISBN search if a DOI search fails