Update book web page

I have updated the web page for my book, PostgreSQL: Introduction and Concepts:

http://www.postgresql.org/docs/awbook.html

I have added a section for 7.1 changes, two new chapters, and some web
links, including a link to the new German translation.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026