Add @Validate to all API implementations

RMB automatically validates a request against the .raml and .json schema specification provided that the method that implements the API has a @Validate tag added.

Some methods have this tag, most don't.

Adding this tag will ensure that all clients actually comply with the API spec. Otherwise a requests will be rejected with a detailed error message.

This doesn't introduce new requirements, the interface spec is still the same. It simply activates a strict enforcement of them.