Cluster registration clientconfig (#135)
* use ListClustersPages for better paging expression
* changelog
* Add option for providing in-memory kubeconfigs.
* implement as oneof
* add *rest.Config as another option for master kubeconfig
* tweaks
* rework KubeCfg
* fix remote context bug
* Merge branch 'master' into cluster-registration-clientconfig
* changelog
* Use clientcmd.ClientConfig for everything
* Restore RemoteCtx because of open issue.
* gen code
* restore remote kube context in tests
* update changelog
