Put a Prerequisites section in all the hosted gettting-started-guides. Change how title and contents are formatted so they are not automatically included in the ToC. Tweak other section headers to improve ToCs.
hack/run-gendocs.sh puts ga-beacon analytics link into all md files, hack/verify-gendocs.sh verifies presence of link.
Fixes #6965 Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
