builder: Replace fedora-<NN> shell & kickstart with a single script.

Just use:

  ./fedora.sh 18

Note that you don't need to be root.
builder: Replace ubuntu-<NN>.sh with a single script.

Just use:

  ./ubuntu.sh 10.04 lucid

Note that you don't need to be root.
builder: Replace debian-<NN>.sh with a single script.

Just use:

  ./debian.sh 6 squeeze

Note that you don't need to be root.
builder: Replace centos-6.sh with a single script.

Just use:

  ./centos.sh 6

Note that you don't need to be root.
builder/website: Add validate.sh test script to EXTRA_DIST.

This fixes commit 154bfb7dd46e7998eed1d40ead95923590763739.
Don't include email addresses in AUTHORS file.

Some authors had duplicate entries because they had multiple
email addresses.
Version 1.25.5.