[poppler] queries via poppler API

[Jack Tanner]

How easy should it be to use libpoppler to run reports about PDFs in 
one's library (rather than using libpoppler to render the PDFs)? For 
example, I'd like to be able to run queries like these:
- What PDFs consist entirely of images and no text?
- Who are the authors of the PDFs?
- Reset the 'author' of the PDFs in this folder to the string following 
the first heading.
- Given the support for annotations discussed earlier, what PDFs have 
annotations?

Thanks!