Medium: NodeUtilization: Add NodeUtilization agent

The Node Utilization agent detects system parameters like available CPU, host
memory and hypervisor memory availability, and adds them into the CIB for each
node using crm_attribute. Run the agent as a clone resource to have it populate
these parameters on each node.

Note: Setting hv_memory only works with Xen at the moment, using the xl or xm
command line tools.