Referer remove HTTP referer information before it's sent to the web
server.  Referer information tells web servers the web page you were
at right before you accessed the current page.  In many case this can
be a useful feature but under some circumstances it might reveal
private information that users may not wish to disclose.

This filter can change the Referer to any string or remove the Referer
header entirely.  For fun it you might want to set the Referer to
http://www.webpagesthatsuck.com/.

This filter has the following configurable preferences:

* Referer.referer

  Referer value to sent.  A value of NONE will cause the Referer
  header to be removed.

* Referer.allowSameDomain

  Allow unmodified referer information if both the requesting URL
  and HTTP Referer are in the same domain.
