Enable Citations to literary works

[bohungi]

This is a must have. We had touched upon this topic in earlier conversation. I forget now: Did we already design an approach? If so, we should probably talk about it before development progresses.

If we did not design an approach already, I have an idea how we could get a something that works for version 1 and, hopefully, is not too complex to implement.

[xqiu1]

• [x] create global citation database (similar to newcommand)
• [x] <cite></cite> when type, show choices of citation (similar to cross reference) - display initials as default
• [x] hover the citation text, display authors, title, and year of publication
• [ ] book keeps a reference list