new NCBI Nucleotide web translator

Using the Entrez Eutils JSON API. This is a translator for datasets, and therefore has some limitations, e.g. apparently no author information.
This has caused issues before. You need to make sure that the title and the id are coming from the same node (`//div[@class="rprt"]/div[@class="rslt"]`, you can also probably just use `var results = doc.getElementsByClassName('rslt')` to get all the relevant nodes). So the idea would be to get all the results first, then traverse and get title/id from each, skipping any nodes where either of those does not exist. Using separate xpaths as above can lead to mismatched titles/ids if one of them is missing in the list, which could be worse than not offering to import the item at all.