[Data-modeling] Cleanup of types the /book domain

[Bryan Cheung]

Now that the /book domain refactoring is complete, there are a few  
types that are no longer necessary that I would like to delete.  They  
are:

/book/editor
/book/reviewer
/book/interviewer
/book/magazine_cover_artist
/book/book_illustrator
/book/book_cover_artist

These types have been replaced by the /book/authorship and /book/ 
illustration_instance CVTs.

More details about the refactoring can be found on one of the old  
emails that was sent in February:

http://lists.freebase.com/pipermail/data-modeling/2008-February/000361.html

Anybody still using these types or have an objection to removing them?

Bryan