Add check on long author-strings in RIS (and related)

[adam3smith]

Several sites add long author strings into RIS AU - tags. Most commonly as
AU - Adam Smith, Karl Marx, Max Weber, Jürgen Habermas
This breaks all sorts of things for import. We can probably recognize at least the most problematic such fields and break them up.
ToDos:

1. Get some example data -- I think there are some exports on the forum
2. Decide on right number of Commas to split. I think the decision would be between >1 or >2. >1 Might incorrectly catch something like, Smith, Adam, Jr. (which I think Zotero itself might export?)
3. Decide on the translators. RIS definitely, but there might be a couple of others to look into like Refer