Service Definitions

AWS doesn't support the concept of composite security groups, so you have to specify a list of security groups you want to associate with an instance when you launch it. This patch adds the concept of a "service" which is basically that list of security groups. The holepunch CLI has been augmented to support querying the groups in a service. Currently the output is comma-delimited so that it can be easily passed to `knife ec2 server create`.