Adds Nat64InfoModule which resolves IPv6 addresses for IPv4 addresses
in IPv6 only network where jitsi-meet deployment does not provide any
IPv6 addresses as ICE candidates.

The onPresence parsing was refactored to remove use of jQuery.
This exposed three methods not available in react-native:
ParentNode.children, ChildNode.remove, and
document.querySelectorAll. The querySelectorAll change could
be swapped for the already polyfilled querySelector, but
children and remove had to be added. The polyfills are based
on those supplied by MDN web docs, but modified to pass jitsi
linting.

Moves the things around to be able to override the config with the URL
params specified in the hash part of the location URI to which the app
is navigating to.

Updates react-native-webrtc to get rid of Java 8 requirement for
the Android app.

Recent changes in lib-jitsi-meet probably led to (1) our
RTCPeerConnection customizations on react-native not being used which is
a problem because we need them for at least NAT64 on iOS in order to
pass the review in Apple's App Store and (2) unexpected exceptions
inside react-native-webrtc.

The Promise-based WebRTC API should be merged from react-native-webrtc's
upstream but I don't want to do it right now because last time we got
multiple bugs in addition.

[RN] Fix PR feedbacks, write persistency docs

These modification are not necessarily directly related to the
containing PR, I merely saw them while reviewing the containing PR.

Do the selection in mapStateToProps so the container itself doesn't need to
receive all the props that each overlay needs.

Each overlay is responsible for fetching their own props and for providing a
"needsDisplay" static method wich will be called with the full redux state and
should return true if the overlay needs displaying.

Also eliminate duplicated state keeping: the connection and conference error
states can be fetched from their respective base features.

* Adds initial documentation for sipgw jibri.

Also explains enabling the people search service and the request/response that are made around sipgw jibri service.

* Fixes add people dialog to invite users and rooms.

No invitation is sent when there is nobody to invite.

* Reuse some recording strings, by using arguments.

* Make sure web also dispatches CONFERENCE_WILL_JOIN.

* Introduces new feature videosipgw.

* Fixes lint errors.

* Renames methods to use people, chatRooms and videoRooms.

* Updates to latest lib-jitsi-meet (dc3397b18b).

Everything strophe related is now handled in lib-jitsi-meet project.

ESLint 4.8.0 discovers a lot of error related to formatting. While I
tried to fix as many of them as possible, a portion of them actually go
against our coding style. In such a case, I've disabled the indent rule
which effectively leaves it as it was before ESLint 4.8.0.

Additionally, remove jshint because it's becoming a nuisance with its
lack of understanding of ES2015+.

* Javadoc introduced @code as a replacement of <code> and <tt> which is
  better aligned with other javadoc tags such as @link. Use it in the
  Java source code. If we switch to Kotlin, then we'll definitely use
  Markdown.

* There are more uses of @code in the JavaScript source code than <tt>
  so use @code for the sake of consistency. Eventually, I'd rather we
  switch to Markdown because it's easier on my eyes.

* Xcode is plain confused by @code and @link. The Internet says that
  Xcode supports the backquote character to denote the beginning and end
  of a string of characters which should be formatted for display as
  code but it doesn't work for me. <tt> is not rendered at all. So use
  the backquote which is rendered itself. Hopefully, if we switch to
  Markdown, then it'll be common between JavaScript and Objective-C
  source code.

Gradually, we exploded the error of CONNECTION_FAILED in multiple
redux state properties. The explosion makes maintenance harder because
the properties have to be updated in sync. Collect them in an object
resembling an Error instance.

It's built on top of React Native's AsyncStorage. They have differing APIs, so
we implement a synchronous API on top of an asynchronous one. This is done by
being optimistic and hoping that operations will happen asynchronously. If one
such operation fails, the error is ignored and life goes on, since operations
are performed in the in-memory cache first.

Note to reviewers: LocalStorage.js lacks Flow annotations because indexable
class declarations are not yet supported:
https://github.com/facebook/flow/issues/1323 and yours truly couldn't find a way
to make the required syntax work without making it unnecessarily complex.

In order to load the configuration from the shard that will actually
host the conference, it's imperative that we add the room= query
parameter:

https://meet.jit.si/config.js?room=example

This implies a departure from our current model, where the config is
discarded if the domain for the next conference is different, but kept
otherwise.

* feat(analytics): move to React

The analytics handlers have been moved to JitsiMeetGlobalNS, so now they are
stored in `window.JitsiMeetJS.app.analyticsHandlers`.

The analytics handlers are re-downloaded and re-initialized on every
lib-jitsi-meet initialization, which happens every time the config is changed
(moving between deployments in the mobile app).

* Adds legacy support for old analytics location.

The global.performance.now polyfill is removed since it's polyfilled by
react-native-callstats.

Currently lib-jitsi-meet looks there in case the `anonymousdomain` config option
was specified.

While this commit alone doesn't add support for authenticated deployments, it
avoids a failure if `anonymousdomain` was set, regardless of authentication being
turned on or not.

Fixes: https://github.com/jitsi/jitsi-meet/issues/1858

Apparently iOS doesn't like dangling background tasks very much, so update the
background timers plugin with a version which fixes this.

https://github.com/ocetnik/react-native-background-timer/pull/38

Also accomodate for the API changes upstream.

Credits to @lyubomir for finding the needle in the haystack.