Add port range iptables rule

to be more complete and not have to look it up every time.
add mention of fetch-crl
Add convertion of host key
make sure the defaults are not too strange

The MySQL section was super confusing. I think it would be even better to have something that makes this example fail...
add the iptables save command

Allows to have direct application of the iptables without reboot (certified to work on slc6)
Merge pull request #31 from sposs/patch-4

Add port range iptables rule