moderatedcomments: Added moderate_pagespec

moderatedcomments: Added moderate_pagespec

* moderatedcomments: Added moderate_pagespec that can be used
  to control which users or comment locations are moderated.
  This can be used, just for example, to moderate http://myopenid.com/*
  if you're getting a lot of spammers from one particular openid
  provider (who should perhaps answer your emails about them),
  while not moderating other users.
* moderatedcomments: The moderate_users setting is deprecated. Instead,
  set moderate_pagespec to "!admin()" or "user(*)" instead.