Provide the plugin user with more visibility into the available VCH Management API servers

[wjun]

As described in vmware/vic-product#1952, provide the plugin user with more visibility into the available VCH Management API servers.

This likely involves replacing the initial landing page of the plugin which currently has a single-row datagrid. (Or removing that page entirely and adding a tab on the next page of the plugin, between "Summary" and "Container Hosts" which provides information about the available OVAs.)

This may involve allowing a user to select which of several compatible OVAs should be used.