[Zope] Prevent cache from being loaded in Zope/DTML

[Oliver Bleutgen]

> Not all caches will respect the Expires: 0 form of the header.  You
> should also add pragma: no-cache, which will hit all of the older
> browsers.

Hehe, 
this reminds me of an incident I had with a project.
I had Expires: -1d set in the header and when trying to print
with netscape it printed a nice html-page saying:

This page has expired, please press reload.

cheers,
oliver