Instead of bundling it in lib-jitsi-meet, which unnecessarily increases
lib-jitsi-meet's bundle size, polyfill it here so it's available in the global
scope, just like the web does.

- navigator.{platform,plugins} were needed by the no longer existing screenshare
  adapter
- document.implementation is already polyfilled by xmldom

They were required only on Android because of its old JSC version. With the JSC
version bump they are no longer required.

The previous location no longer exists. This is a fork of the original package,
which is actively maintained.

Fixes: #3304

It's required by lib-jitsi-meet when using WebSockets.

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.

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

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.

* 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.

Includes automatic recommended Xcode project file fixes.

Lib-jitsi-meet uses jQuery's .append method to manipulate Jingle. The
method in question invokes the getter and setter of Element.innerHTML.
Unfortunately, xmldom which we use in React Native to polyfill DOM does
not polyfill Element.innerHTML. So polyfill it ourselves.

Turns out React Native's timers (setTimeout / setInterval) don't run while the
app is in the background: https://github.com/facebook/react-native/issues/167

This patch replaces the global timer functions with those from the
react-native-background-timer package, which work in the background.

These timers won't magically make an application work in the background, but
they will run if an application already happens to run in the background. That's
our case while in a conference, so these timers will run, allowing XMPP pings to
be sent and the conference to stay up as long as the user desires.

jitsi/lib-jitsi-meet#66b601e disabled the execution of Temasys'
adapter.screenshare.js on browsers on which we don't use Temasys such as
React Native. Henceforth, no Temasys workarounds are necessary on React
Native.

As an intermediate step on the path to merging jitsi-meet and
jitsi-meet-react, import the whole source code of jitsi-meet-react as it
stands at
2f23d98424
i.e. the lastest master at the time of this import. No modifications are
applied to the imported source code in order to preserve a complete
snapshot of it in the repository of jitsi-meet and, thus, facilitate
comparison later on. Consequently, the source code of jitsi-meet and/or
jitsi-meet-react may not work. For example, jitsi-meet's jshint may be
unable to parse jitsi-meet-react's source code.