Working iteration of cluster roles

This pull request has several additions, fixes and improvements to the CREAM-CE, WN, and head-node roles.

We also start using the Ansible Vault for passwords.

This has been tested a few times on the ZA-MERAKA cluster.

functional tests have been made a few times, but not implemented (ie, ops jobs run :grinning: )

Time to pull this into the master branch, plus it's friday.