Add a dashboard switch mechanism

[leograba]

This app displays a dashboard in Chromium in kiosk mode.

Adding a mechanism to switch the dashboard on the fly will allow to have more than one dashboard and periodically rotate the current one being displayed.

There may be more than one way to do it, for example https://stackoverflow.com/questions/31340063/how-to-change-url-on-chromium-kiosk-mode-via-ssh

[leograba]

Another possible way is via the commands API: https://stackoverflow.com/questions/30857390/using-the-chrome-commands-api-in-kiosk-mode?rq=3

There may also exist easier options to solve this specific problem: stop the Chromium container and restart with the new URL.

[leograba]

Or also use some sort of process manager inside the container to only restart Chromium https://github.com/just-containers/s6-overlay

[leograba]

The current approach of forcing the container to restart is too dirty, and it seems that for an unknown reason the board reboots after some restarts.

Instead of try to debug the symptom of the dirty approach, let's try to use a more clean one.