Disable per-node SG generation
Do not delete unknown SG rules
Disk layout improvements for hs1.8xlarge

This makes sure that all 24 disks are setup, forces partitioning from
amazon and generally make the layout work better.
Merge pull request #1 from orchestrate-io/device_names

Use partition names in device maps.
Add mappings for m1.xlarge and hi1.4xlarge
Merged changes on block_mappings