Support all IWC Best Practices rules

[davelopez]

This issue will track the implementation of all the validation rules needed to comply with the IWC best practices.
These rules will be included in the iwc validation profile:

• Check for the release property to be defined.
• Check that all workflow outputs have labels. #41
• Check that content_id, tool_id and tool_version are in agreement. #42
• TODO Add more here...