New c4 nodes

The cluster has grown!
We removed the c0 nodes (and thus the high_mem queue), that were the oldest ones in the cluster.
We installed a new rack (rack 4). The new sixteen nodes (c4-0 to c4-15) in this rack feature 32 cores each. Additionally, a gigabyte of memory is available to ALL the jobs that will run there, that is, as much as with the previous high_mem queue.

This adds 512 new cores to our cluster, now composed of almost
1100 CPU cores. Enjoy! :)