ec2_asg: Added a more verbose response to the module.

Now includes its settable attributes and a list of its instances

Response like:
```
TASK: [ec2_asg ] ************************************************************** 
ok: [localhost] => {"availability_zones": ["us-east-1a"], "changed": false, "desired_capacity": 1, "instances": ["i-e9038fb9"], "launch_config_name": "dx_auto-deploy_test_lc", "max_size": 2, "min_size": 1, "vpc_zone_identifier": "subnet-c9c906a8"}
```