Only one notification will be displayed at a time on mobile.

Adds 1 liner notifications to mobile. Only the title is displayed. In
case the title is missing there's a fallback to the description.

Moves NotificationContainer to the toolbox and filmstrip container, so
that there's no need to manually calculate the positions.

The outer container is not necessary if 'justifyContent: flex-end' is
used with the absolute fill on the main container.

* feat(notifications): implement a react/redux notification system

* squash into impl explicit timeout, style

* ref(notifications): convert toastr notifications to use react

* ref(toastr): remove library

* squash into conversion: pass timeout

* squash into clean remove from debian patch

left blank in default meet installations, to be overridden by adding <base href="CDN_URL"> to /base.html