Add support for Eucalyptus endpoints

- Interpret edda.region or edda.$account.region as a hostname
  when it is not an AWS region name.
- Use EC2 region's DNS name existing as test for AWS region existence.
- AwsClient.setEndpoint construct Eucalyptus URLs if not an AWS region.
- Supported: AutoScaling, CloudWatch, EC2, ELB, IAM, S3
- Unsupported: ElastiCache, RDS, Route53, SQS