Contrib docs v1

I attach the patch for the contrib docs. Mainly it's been formatting the
README files of each directory into SGML.

I've removed TODOs, history, licenses (all of them are BSD AFAICS), file
descriptions and install instructions (I only left one for them all).

The hole contrib is one single chapter after Full Text Search. I think this
gives it a lot of visibility as it's where other functions are, and given
that most contrib modules provide functions seemed a good place. However, Tom
showed some concerns with that so a final position should be decided. Each
section is the name of the contrib module. The first paragraph summarises
what it does. And usually the last subsection contains the author(s). The
rest is pretty different from one another and possibly some polishing will
have to be done afterwards.

--
Albert Cervera i Areny
http://www.NaN-tic.com