Add example site-config.cfg, with sanity testing definitions

Publish a version of the daily regression jobs configuration,
so people have a starting point to assemble their own
KVM testing farm. This will be referred by the
RegressionTestingFarm documentation on virt-tests.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
site-config: Remove guest OS that are not publicly available

We had Windows 7 and RHEL 6.3, that not all people have
access to. So let's replace them by Fedora 18.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>