Add elasticbeanstalk_env module

A new module that can create, update or terminate an Elastic Beanstalk application's environment. It also deploys a given application version.

Unfortunately, specifying the following parameters does not work because of issues in boto:
- options_to_remove (https://github.com/boto/boto/issues/2327)
- tier_name, tier_type or tier_version (https://github.com/boto/boto/pull/1911)

Please advise how to handle these issues.