cloudcaster multi-group support

- attaches list of security group IDs to LC / interface
- also updates ec2createapp to also attach list
multi-group support for cloudcaster

- fix an iteration in early code committed before testing
- only post a secgrp once to the list of security groups
Merge pull request #38 from WrathOfChris/cm-cloudcaster-multigroup

cloudcaster multi-group support.

new app.groups list parameter that allows additional multiple security groups to be added to an instance.