Allow an internal pod template reference or object

Extracted from #1600, starts #170
Updated with all comments made so far.

----- Original Message -----
> Yeah, round trip should catch all of these things (although I'll double check
> that our initialization doesn't hide that).  We're not protected today from
> making a field round-trippable (adding it to the old api) but the fuzzer
> just nils it each time.  A negative round trip test should be done... but
> it's a lot of work.
> 
> ----- Original Message -----
> > >  				return err
> > >  			}
> > > +			out.CurrentState.Replicas = in.Status.Replicas
> > 
> > hm-- this is asking for a subtle bug if another field gets added to Status.
> > I
> > guess our fuzz test will catch it.
> > 
> > ---
> > Reply to this email directly or view it on GitHub:
> > https://github.com/GoogleCloudPlatform/kubernetes/pull/2195/files#r20173444
>