[Rpm-metadata] updates

[seth vidal]

> It seems to me that it would be useful to have a more static file that
> describes the repository and points to a this file that contains the
> entries about the actual metadata file.

Some more information here:
A repository might look like this:
/myrepo/repository.xml
        repomd.xml.gz
        primary.xml.gz
        filelists.xml.gz
        other.xml.gz
        groups.xml.gz

primary, other and filelists are generated from the rpms
groups is the file we described before for groups of packages
repomd contains timestamps/checksums for the other xml.gz files
repository.xml contains the name, contact, description, keywords, etc
info for the repository. This is not gzipped to be more human readable
and b/c it will be obviously small.

There has been an ongoing discussion on other lists and irc
channels(mostly having to do with fedora, admittedly) on how to do
repository mgmt so user's don't need to edit config files to add a
repository, this is why I'm bringing this up here.

comments appreciated.
-sv