Support for subnet 'names'

several users have expressed an interest in having names for some subnets as well. These may be locations, building IDs, department codes or a combination. They want this to come from Kea, from the configuration, so this requires a Kea change as well.

Users with a large number of subnets may also want to specify which subnets should be displayed on the dashboard, as there will be a few 'problem' subnets and those may not - probably will not be, the largest subnets.

This is the last remaining issue from GL #374 (closed), notes from the second user test.

Most enterprises are going to want a field for geographical location (which might be Kansas City, or DC3), and many will also want a logical tag that might identify a service (public wifi, bldg security, etc). We should think about providing at LEAST one field for this kind of data, and ideally two - location and service or role.

I know there is a concern about the real estate for the listview rows. We may have to add the ability to show/hide some columns to accommodate these added fields.

It would also be very useful to be able to filter on the values of these fields (e.g. show all servers or all subnets in Kansas City, or show all servers or subnets associated with building security). This is because if you have a problem, it may be specific to a location or a service.