Description of problem:
All Fedora trademarks need to be kept in a single package, the fedora-logos
package as a matter of legal policy.  We also need to do this to make it easier
for people to be able to respin and rebrand derivatives using revisor/wevisor.

What needs to be done? 
*We need to get the powered by fedora logo into the fedora-logos package. I'll
open a second bug against fedora-logos.

*This package needs to require system-logos.  The idea here is that people can
include their own package which provides system-logos using non fedora marks as
replacement images for fedora-logos.

*Optionally provide a technical mechanism to fallback to an included default
image that does not include the fedora marks if the fedora-logos package is not
installed.

Also it appears that http also includes fedora marks in its package. It might be
worthwhile to use the same mark between both packages if it makes sense.