The welcomePageEnabled and pictureInPictureEnabled props on mobile have been
converted to feature flags.

If audio-only was engaged, use the video (un)mute button to disengage it. This
should simplify the flow for getting back to video.

Re-structure the custom routing to split between
platforms instead of between intended route features.
This made it easier for me to understand where to
do the checks for unsupported browser after deep-linking
had been checked.

If a value is not set in localStorage then null is
returned. null should not be converted to an empty
string (via _.escape) because that will then be
stored in localStorage as the user set preference
and will keep overriding any other values set
in localStorage for the displayname.

- Use actions to notify the rest of the app that
  a mic or camera error has occurred
- Use middleware to respond to those notifications
  of errors by showing in-app notifications and
  notifying the external api

When in a conference, try to enter PiP when pressing the back button. If this is
not possible (because it's unsupported, not enabled, etc.) fall back to the
previous behavior of simply hanging up.

This PR changes the logic for connecting / disconnecting conferences. Instead of
doing it in mount / unmount events from the Conference component, it moves the
logic to the appNavigatee action.

This fixes a regression introduced in 774c5ecd when trying to make sure the
conference terminated event is always sent.

By moving the logic to appNavigate we no longer depend on side-effects for
connecting / disconnecting, and the code should be more maintainable moving
forward.

An improvement to this is the concept of sessions, which, while not tackled
here, was taken into consideration.

* Groups devices notifications by type audio/video.

* Fixes passing correct device array.

For the external api to fire update events out of the iframe, it
must first be initialized within the jitsi app. Any invocations
by the app to send updates events before initialization will
cause the api to swallow the events. The chosen fix is to
initialize the api earlier so the first update of app's redux
store fires update events that the api will also fire out of
the iframe.

This change will affect current behavior in that right now
the update event of the initial set of the avatar url is
blocked, but the change will make that event fire out of the
iframe.

Currently devices set through the api are stored
as ids, and not user selected. This can cause
other existing user selected devices to take
precedence over the devices passed into the api.

Method blur is not called. Method blur is called
internally only.

This reverts commit 890151fa72.