Some confusion on repos

[Christopher Beland]

I've added a summary of the explanations given here to:

 https://fedoraproject.org/wiki/Releases#Development

I trust others more in the know to review this to make sure it is
accurate.

At some point, information about the Branched phase needs to be added to
https://fedoraproject.org/wiki/Fedora_Release_Life_Cycle and
https://fedoraproject.org/wiki/Releases/Rawhide but since there's
already a demonstrated need for better publicity of the change, I
thought I'd get the wiki update ball rolling.

-B.