Add CSE C-N style. Tweak other CSE styles.
* "Anonymous" is explicitly prohibited in the 8th edition of the manual: "If no author can be determined for a document, omit authorship from the reference. The use of “anonymous” is not permitted."
* Re https://forums.zotero.org/discussion/38245/cant-find-cse-citationnumber/
Merge pull request #1023 from aurimasv/cse

Add CSE C-N style. Tweak other CSE styles.