Optionally allow Chromium Addons

[yulipumal]

Unfortunately, currently Chromium addons are disabled in grafana-kiosk.
Chromium addons would be very handy for some additional features for grafana and the input.

Addons are active, if chromium is started directly from cli
chromium-browser --kiosk $url

[briangann]

will take a look, incognito mode might be doing this

[aholen]

Also the UserDataDir is different for every startup, so I think that needs to be fixed to persist addons #124