Display group of dashboard using tabs

Originally from: https://github.com/influxdata/chronograf/issues/2823

Hello!

Time to time you have more than one dashboard under the same group. Currently, my use case is a group of dashboards like:

* Kubernetes Ingress
* Docker Container
* Kubernetes Infra

These dashboards have two environments, I switch between these envs using template variables. So all good but I would like to group them and switch between these dashboards from inside a dashboard. How I imagine it is a set of labels between dashboard title and the actual graphs:


The image takes part at "The worst screen award" but it's the best one.

The issue describes adding tabs between the dashboard title and graphs so users can switch among dashboards in one group. No source files, tests, or entry points are named, so first locate the dashboard group and rendering code. Done means grouped dashboards can be selected from the tab labels while retaining the existing environment template-variable behavior.

Written by the indexing model from the issue text.