Add a resource fit predicate.

Not linked into any scheduler yet.
Fortunately we don't expose v1beta3 yet and can still freely change it.  The long refactor has at least had some benefits.

----- Original Message -----
> > @@ -565,6 +574,9 @@ type Node struct {
> >  
> >  	// Status describes the current status of a Node
> >  	Status NodeStatus `json:"status,omitempty" yaml:"status,omitempty"`
> > +
> > +	// NodeResources describe the resoruces available on the node.
> > +	NodeResources NodeResources `json:"resources,omitempty"
> > yaml:"resources,omitempty"`
> 
> Actually, the Capacity field of NodeResources belongs in Spec. NodeResources
> doesn't make sense.
> 
> Sadly, I didn't have time to vet resources.md at the time it was written. I
> should fix it.
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/GoogleCloudPlatform/kubernetes/pull/1474/files#r20533015