READY FOR TESTING: chef-metal 0.11 support

Supporting the new chef-metal 0.11 release:
* Parallelization via machine_batch (used in the cloud_create action)
* New nicer chef-client run output
* New cleaner driver interface with chef-metal 0.11
* improved region handling
* Enable the `metal` command to understand our SSH key scheme
* Improvement to enable multiple ec-metal instances (directories) to run in parallel by automatically finding available TCP ports for chef-zero and decentralizing the `chef-client-running.pid`