Book and inproceedings forms

The forms show the correct required and optional fields now, and the required new models (e.g. series for book) have been generated. The forms don't actually work though, since ReferencesController create method is currently tailored for articles. The next thing to do should probably be implementing new create methods for different types of references.

A question to ponder - is super_reference actually better than having a table for each reference type separately? It is quickly becoming huge & really complex..