[CNKI] complete rewrite

Re https://forums.zotero.org/discussion/31522/articles-in-chinese-databases/

Uses Refworks export feature. Supports search results and individual items on the Chinese and "oversea" version of cnki.net

Re https://forums.zotero.org/discussion/27851/translator-for-cnki/ we can use the same method to fetch metadata, but the results are in Chinese. I'll need to mess around and see if we can get them in english somehow. The data clearly exists...

Also partially satisfies https://forums.zotero.org/discussion/12129/wish-to-add-a-new-chinese-cnki-translator/

No PDF attachments (yet). I can't find any that I have access to, so I can't say if there is an intermediate page we need to worry about. The code is mostly there, it's just commented out.