Majorana upgrade

In the last days, the cluster has been updated. As usual, report to cluster_admins@iridia.etc any issue, problem, lack of docs, that you encounter.

List of the changes:
* the OS is Rocks 6.2, based on CentOS 6.2
* a new rack (number 5) has been added. It is composed of 4 computational nodes (from c5-0 to c5-3), each with 24 cores, for a total of 96 new slots added to the cluster. Each one of these new cores is roughly 3 times faster than the nodes in rack4. It has also more memory, so each job running on a node of rack5 can use up to 2.4GB of memory. To see how to use the new nodes, take a look at cluster composition and how to submit a job. Enjoy responsibly.
* due to power considerations, we had to remove 8 nodes of rack1, which now has 32 cores available, in the nodes 7-12, 14, 15.