* iam_group: (integration tests) migrate tests to module_defaults
* iam_group: (integration tests) migrate to using temporary user and group with {{ resource_prefix }}
* iam_group: (integration tests) fix test, checking the return values
* iam_group: (integration tests) Add some more tests around the behaviour of 'changed'
* iam_group: (docs) Update documentation of iam_group return value
* Update AWS testing policies to enable group/user management
* Improve iam_group exception handling
Use AnsibleAWSModule for iam_group and handle BotoCoreErrors
as well as ClientErrors. Use fail_json_aws to improve error messages
* Add minimal iam_group test suite
Update some of the read-only IAM permissions (this is not sufficient
to run the test suite but it gets further than it did until it tries
to add a (non-existent) user)
* Clean up after tests
