Create links between VPN resources

This commit creates cross links between VPN resource
and resolves VPN related resource UUID to its name.
This helps users to track VPN resources.

Closes-Bug: #1222264

This commit also improves an error handling when an error occurs
during retrieving a resource detail via API call.
While previously a detail page without item values is displayed,
now the index page is displayed for such case.

Change-Id: I53e03bf01ad0f359b889115068b1548c9a61ae8d
Merge "Create links between VPN resources"