more metadata options

We use this for our cloudformation scripts so why not share

* more options added for InitFile, made content optional
* added InitService and InitServices with an example of using it
It's referring to this:
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-init.html#aws-resource-init-services

Looks like packages could be added to it as well. The distinction between "actual function" and "helper function" is probably nuanced by the inclusion of a CF type. So yes, I would consider this a useful helper function.