WIP: RFCxxxx Class-based PSDSC resource contract for DSC v3

[theJasonHelmick]

No description provided.

[gaelcolas]

I'm unsure about the Attributes and metadata, mostly that those should not be relied upon by the adapter, since it should be defined in the resource manifest.
@michaeltlombardi don't we think that should be done by the resource manifest anyway, and the attributes are only relevant to generate the manifest? (so they're out of scope for this RFC, but the manifest metadata should be in-scope and clarified here?)

Another thing I think is missing is how we could get the same outcome as the Machine Config "reasons".
I think the return object [System.Tuple[bool, <ResourceClass>, String[]]] is simplistic, or should at least explain how the [string[]] are used/displayed through the adapter and engine.