A way for operators to attach a virtual host description

[michaelklishin]

Currently in deployments with a lot of virtual hosts that do not follow any naming conventions
it is quite difficult to map a virtual host to an app/pod/set of apps/environment/what have you.

It would be useful to have a way to provide a description for a virtual host, and possibly even tags.

Per discussion with @mkuratczyk.

[michaelklishin]

This turned out to be moderately difficult because it changes the schema of a distributed table, so we have to use a feature flag and a new virtual host field acceess module, à la amqqueue for queues. Unlike amqqueue, this seems to be a significant overkill. If this takes longer than a two day spike we'll close this issue as a wontfix.