Andy's catalog fix script

Hi!

This message mainly concerns Andrew Altepeter, but I reckon some others 
may have an opinion too...

Andy has written a howto and a script to solve certain catalog issues 
(POSKeyError), which we examined to see if it can go into the Silva 
core. However, personally I would like to see some changes before this 
happens:

- Currently part of the solution is in a howto, and I think this can be 
scripted too. It would be nice if the script would be extended to 
perform a larger part of the fix (cleaning up and rebuilding the catalog).

- I think some things are hard-coded that can be generated (meta_types 
in the script for instance can be retrieved from Silva/Zope by checking 
what implements both ISilvaObject and ICatalogPathAware or something).

If those issues would get fixed I'd love to add it to the Silva core, 
for now however I reckon just pointing to the howto from Silva's docs 
would make more sense... What do you people think?

Cheers,

Guido