Reorganize and improve exit relay docs
Added titles, add openSUSE exit doc, and change instructions about QNAME minimisation since it became the default
- /content/relay/setup/exit/opensuse/contents.lr
- /content/relay/setup/exit/debian-ubuntu/contents.lr
- /content/relay/setup/exit/centos-rhel/contents.lr
- /content/relay/setup/exit/freebsd/contents.lr