[#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.
For all of these, I would remove the `this`, so 'configure EdgeGateway', 'get the vCloud Attributes for EdgeGateway'. The `this` is implied, and it slowed me down a bit.

Also, for this one, might be worth mentioning that it goes ahead and posts the config whether or not it's the same as is already there? Didn't phrase that very well