[Rivet] Code documentation

[David Grellscheid]

Hi Frank,

> didn't survive the HepForge change very well... is that just because
> it's looking for a style sheet which is now at a different location?

It's looking for a projects.hepforge.org/common directory which was 
retired. The Doxygen needs to be regenerated anyway as full html pages, 
so the path to a new, local stylesheet can be added then.

I don't know who built the docs last time.

See you,

   David