[#75691732] Document vcloud-core public methods

> According to semver http://semver.org/ we should document the API
> (lower case should). We should document this by adding Yard
> documentation to public methods. See [#73962736] for an example.
I can't see what you mean @annashipman - I know what you mean, but I don't see what the documentation should be to mark a parameter as optional.