Remove 'incomplete' from the spec and libs

[Polleps]

The spec details that resources can be marked incomplete.
From what I can see it was only really meant for when dynamic properties are not set by the server.
However we never use it and the server even ignores it when get_resource_extended is called with skip_dynamic set to true:

/// - *skip_dynamic* Does not calculte dynamic properties. Adds an `incomplete=true` property if the resource should have been dynamic.
 fn get_resource_extended(
        &self,
        subject: &str,
        skip_dynamic: bool,
        for_agent: &ForAgent,
    ) -> AtomicResult<ResourceResponse> {
        let _ignore = skip_dynamic;
        let resource = self.get_resource(subject)?;
        hierarchy::check_read(self, &resource, for_agent)?;
        Ok(resource.into())
    }

I think we should just remove the whole concept from the spec