Extend kubectl-operator plugin to support ClusterCatalogs

[ankitathomas]

Extend kubectl plugin to support commands for ClusterCatalogs including:

• list : list currently installed ClusterCatalogs with useful information including status
• get : get info on an existing ClusterCatalog
• add : create a new ClusterCatalog for a provided image with optional metadata (labels, priority, enabled/disabled, polling interval etc.)
• enable/disable : change the availability of a ClusterCatalog
• remove : remove an existing ClusterCatalog