Update to Babel 7 (needed for RN 0.57 update)

feat(BworserCapabilities): fix device change detection

Safari 11 has `navigator.mediaDevices.ondevicechange` but doesn't define
`navigator.mediaDevices.addEventListener`. 🤦

Fixes: https://github.com/jitsi/lib-jitsi-meet/issues/823

feat(TPC): fix handling layer suspension when RTPSender is not supported

Just skip it in such environments, such as React Native.

deps: js-utils

feat(flow): fix webpack bundling when Flow annotations are used

Refactor permissions

Share code amongst "Chrome-like" browsers

Use the W3C Permissions API where possible. At the time of this writing this is
supported in Chrome >= 64.

The code for handling device availability has been disabled for a long time,
plus it's ill named since it represents 2 abstractions: lack of permissions and
lack of devices.

Time for it to rest in the git graveyard.

We now use PeerConnection promise-based APIs, which were introduced in M51.

This function helps simplify the code when handling browsers that are pretty
much Chrome in disguise.

js-utils has some, so we need the preset or webpack fails with a syntax error.

* feat: Read the server region from Jingle and broadcast it with statistics.

* feat: Adds the bridge count to local "statistics", refactors conference-properties.

* fix: Emits the conference properties with the event, small fixes.

* ref: Orders the imports alphabetically.

As described by @virtuacoplenny:
[T]he ordering is based on import path, not import name, with different
file depths being grouped together, node modules being grouped together
at the top.

* fix: Keeps JitsiConference#properties always defined.

* fix: Does not fire an event when the argument is undefined.

Could not update karma-webpack to latest as it was not running because of an error:
The "path" argument must be of type string. Received type object
https://github.com/webpack-contrib/karma-webpack/issues/350

Chrome fires devicechange twice. This causes the DEVICE_LIST_CHANGED
event to fire twice. The listener in jitsi-meet has async logic
to handle the event, including creation of new tracks. So it
can happen that two devicechange events fire, the jitsi-meet
listener fires twice, creates duplicate tracks, and uses both
tracks. Diffing the device list for an actual change is a workaround
against extra devicechange events.

Note: this does not solve the issue in jitsi-meet of it not
handling quick successive DEVICE_LIST_CHANGED events.

This simple change helps to prevent `'The conference is has been already left'` error after kick. 
`Conference.leave` will detach chatRoom instance itself.

Keeps it consistent with the previous implementation.

When using the Promises API, modern constraints are used, so adapt to it and use
the modern versions.

Just use navigator.mediaDevices.enumerateDevices().

It's 2018 after all...

Get rid of all wrappers and use navigator.mediaDevices.getUserMedia, since all
supported platforms have it by now.

Also use the unprefixed versions of WebRTC APIs.

Emit ACTION_JINGLE_SI_TIMEOUT analytics event if it takes too long for
Jicofo to send session-initiate (it usually arrives within 1 second).

JingleSessionPC cleanup

The previous check looks like it was meant to check if it's
the initiator.