Update documentation that may have changed dramatically over time:

• Update NDS-312 to match new inventory name, node labels etc
• ndslabs-deploy-tools README.md: Need to rewrite almost entirely, make sure to add info about the new node labeling strategy
• ndslabs-startup README.md: Should probably add a bit of info about the new node labeling strategy
• nagios-nrpe README.md: Need to add any information
• ndslabs / gluster / deploy-tools README.md: Add small section of info about workbench node labeling strategy
• cluster-backups README.md: merge outstanding PR (NDS-752), and should also add usage information
• ndslabs gui/README.md: Add additional information about the drop-in functionality?