Don't display DHCPv6 subnets on dashboard if no DHCPv6 apps being monitored
With the Stork 1.0 candidate (using the stork lab set up) the dashboard displays a blank area for DHCPv6 subnets. It would be better to omit that section of the dashboard if the Stork server is not monitoring any authorized DHCPv6 apps. It is a lot of screen real estate to waste in an environment where they are not using DHCPv6 at all.