Made major changes (still in progress to the cluster config)

re-addded the ldap role to the idp-ldap playbook
Closes #45
closes #45
Minor change to the prerequisites needed for debian-based hosts
closes #44
Started working on new WN role
Merge pull request #46 from INFN-Catania/master

Iptables management in a separate role
Fixed iptables also for destination nat

Destination nat requested by tomcat.

This require some additional variable. Chech the role dependencies from fmarco76.tomcat
to see what it is needed