The config object defined by lib-jitsi-meet is not used by
lib-jitsi-meet only, jitsi-meet respects its values as well.
Moreover, jitsi-meet defined classes and/or functions which manipulate
that config object. Consequently, it makes sense to move the config
object and the associated classes and functions in a dedicated feature.

The Device Selection modal consists of:
- DeviceSelection, an overly smart component responsible for
  triggering stream creation and cleanup.
- DeviceSelector for selector elements.
- VideoInputPreview for displaying a video preview.
- AudioInputPreview for displaying a volume meter.
- AudioOutputPreview for a test sound output link.

Store changes include is primarily storing the list of
available devices in redux. Other app state has been left
alone for future refactoring.

On Android the status and navigation bars are shown again after coming back from
the background, so enter full-screen mode again if needed.

The implementation varies across platforms, with the same goal: allow the app to
use the entire screen real state while in a conference.

On Android we use immersive mode, which  will hide the status and navigation bars.

https://developer.android.com/training/system-ui/immersive.html

On iOS the status bar is hidden, with a slide effect.