Canonicalize URLs

It would be great if anemone can handle canonical URLs.

For example, if we enable canonicalization,

  http://www.example.com/index.html
  http://www.example.com/index.asp
  http://www.example.com/index.php
  http://www.example.com/index.cgi?a=2&b=3
  http://www.example.com/index.cgi?foo=bar

should all resolve to:

  http://www.example.com/

and anemone should not download the duplicate pages.

Another example:

  http://www.example.com/search.php?q=how+to+spider
  http://www.example.com/search.php?q=how+to+not+spider

should reduce to :

  http://www.example.com/search.php