Turn Ansible community notice into a warning

Signed-off-by: martin f. krafft <madduck@madduck.net>
Warn about lack of reclass in Salt pre-0.17

Signed-off-by: martin f. krafft <madduck@madduck.net>
Migrate TODOs into documentation

Signed-off-by: martin f. krafft <madduck@madduck.net>