Two complaints about lack of massive setup.exe

[Matt]

> We've had two complaints that people miss the old setup.exe that worked
> "so well".
>
> It would be pretty trivial (thanks to Ron's excellent design) to have
> the current setup.exe pull in all of the non-source tar files and
> extract them.  It would be a huge binary, but if that's what people
> what...

I think we should keep it approximately the way it is, except maybe put all
the packages in one subdir of /latest (like /latest/packages). This new
scheme allows us to do some neat stuff later (like getting only updated
packages).