[Centos] Updates to CentOS-4Beta

[seth vidal]

> 2.  The yum grouplist, groupinstall, groupupdate features have been
> added to the CentOS-4Beta repositories.  Here are some links that
> explain how to use the yum group features:
> 

for completeness sake:
groupinfo and groupremove, too.

in yum 2.1.X, at least.

-sv