This patchset introduces new field to Phase.Config API object
SiteWideKubeconfig - if set to true, the phase will have access
to all kubeconfigs for each cluster defined in ClusterMap.
By default only kubeconfig of the cluster specified in
Phase.Metadata.ClusterName will be available to the phase executor.
This approach will speed up the deployment process because arishipctl
will not have to look for multiple kubeconfigs when running each phase
Closes: #547
Change-Id: Ic92027ba88d3ce8cb769c254968530037540b8fd