Enable v1beta3 API via --runtime_config=api/v1beta3 flag

This exposes the proper v1beta3 API endpoint when the user specifies the --runtime_config=api/v1beta3 argument to the apiserver. v1beta3 is still considered experimental and subject to change.

--runtime_config is a map of string keys and values, that can be specified by providing

    --runtime_config=a=b,b=c,d,e

Only the key must be specified, the value can be omitted.

Enables v1beta3 in hack/local-up-cluster.sh and hack/test-cmd.sh

@bgrant0607

Will allow completion of remaining #1519 items
Found a lot of little issues with v1beta3 conversion round trips - going to resolve those before exposing this


> On Dec 11, 2014, at 7:26 PM, bgrant0607 <notifications@github.com> wrote:
> 
> In pkg/master/master.go:
> 
> >  
> >  	// TODO: InstallREST should register each version automatically
> > -	versionHandler := apiserver.APIVersionHandler("v1beta1", "v1beta2")
> > +	versionHandler := apiserver.APIVersionHandler("v1beta1", "v1beta2", "v1beta3")
> We shouldn't include v1beta3 in this list if it isn't exported.
> 
> —
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