* Update RDS parameter group for boto3
* Update to boto3
* Update to latest ansible standards
* Remove choices list for valid engines (See #19221 for context)
* Allow tagging
* Return some useful information, and document that information
* Add tests for rds_param_group
* Improve testing of rds_param_group
* Add purge_tags option for rds_param_group
* Fix remaining broken rds_param_group tests
* Ensure the group name is lowercased. Fixes integration tests when run on OSX
