Add vc_storagepod resource type.

This add a resource type for creating, editing, and removing Datastore Clusters.  The vSphere API calls Datastore Clusters `storagePods`.  This resource does not support SDRS (Storage DRS), only the creation of a Cluster, addition and removal of Datastores to or from a new or existing cluster, or the removal of an existing cluster.  Datastores removed from a cluster are placed back in the "root" `dc.datastoreFolder` folder.