Aws-parallelcluster

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- feature:``cli``: Introduced sanity_check feature for config
- updates:``cli``: Simplified EC2 key pair config
- feature:``cfncluster``: Scale up is now driven by two policies; enables small and large scaling steps
- feature:``cfnlcuster``: Introduced initial support for CloudWatch logs in us-east-1
- updates:``ami``: Moved deamon handling to supervisord
- updates:``ami``: Pulled latest CentOS errata

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- bugfix:``cli``: Fixed missing AvailabilityZone for "update" command

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- updates:``cli``: Simplfied VPC config and removed multi-AZ

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- updates:``ami``: Pulled latest CentOS errata
- updates:``ami``: Removed DKMS Lustre; replaced with Intel Lustre Client

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- updates:``ami``: Pulled latest CentOS errata
- updates:``ami``: Updated packages to match base RHEL AMI's
- feature:``cli``: Improved region handling and added support for AWS_DEFAULT_REGION

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- feature:``cfncluster``: Added s3_read_resource and s3_read_write_resource options to cluster config
- feature:``cfncluster``: cfncluster is now available in all regions
- updates:``ami``: Pulled latest CentOS errata
- feature:``cfncluster``: Added ephemeral_dir option to cluster config