doc: clarify "B" flag in os recommendations page

We don't exactly do continuous builds on all the platforms marked with
"B", but we have published binary RPMs for them. Adjust the "B"
footnote definition to reflect this.

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>
doc: rm old releases in os recommendations page

Similar to the change in commit
4cdc9c793627eec13c65543c09c604ec27a4dd8a, remove the references to old
Ceph releases.

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>
doc: rm Fedora minor versions in os recommendations

Fedora doesn't have point releases, so it doesn't make sense to talk
about "Fedora 18.0" or "Fedora 19.0" - it's just "Fedora 18" or "Fedora
19".

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>
Merge pull request #3068 from ktdreyer/doc-os-recommendations-cleanup

doc: os recommendations cleanup

Reviewed-by: Loic Dachary <ldachary@redhat.com>