- move extender related API from pkg/scheduler/api to pkg/scheduler/apis/extender/v1
- alias extenderv1 to pkg/scheduler/apis/extender/v1
- use NodeScore and NodeScoreList in non-extender logic
This moves plugin/pkg/scheduler to pkg/scheduler and
plugin/cmd/kube-scheduler to cmd/kube-scheduler.
Bulk of the work was done with gomvpkg, except for kube-scheduler main
package.