A lot of small changes (search-n-replace) make a big commit:

  - fixed update bug in book.module
  - provide a log message when both adding and updating book pages
  - all configurable variables are now accessed through "variable_get()":
  - rewrote watchdog and submission throttle and removed watchdog.inc
  - improved robustness of sections.inc
  - imporved story.module
  - updated ./database/database.sql