test days live image creation guide

[Kamil Paral <kparal redhat com>]

Hello,

our guide for livecd creation used for test days [1] have been
outdated (used F11 packages as a repository). I have rewritten
it to use Rawhide packages for building, which is preferred
for test days. I have also added some info what to do if rawhide
repository is currently broken. Hope that helps.

There is one issue which should be discussed: The default 
kickstart scripts remove fedora-logos package because of
trademark issues with non-official spins. I have added it back
for test days spins. Is that ok? If someone thinks it is not,
it's not a problem to modify it, just tell me.

Kamil

[1] https://fedoraproject.org/wiki/QA/Test_Days/Live_Image