Adds base/sounds feature which allows other features to register a sound
source under specified id. A new SoundsCollection component will then
render corresponding HTMLAudioElement for each such sound. Once "setRef"
callback is called by the HTMLAudioElement, this element will be added
to the Redux store. When that happens sound can be played through the
new 'playSound' action which will call play() method on the stored
HTMLAudioElement instance.

Upstream lacked a CocoaPods podspec file, PR:
https://github.com/DylanVann/react-native-locale-detector/pull/3

Avatars are cached to the filesystem and loaded from there when requested again.
The cache is cleaned after a conference ends and on application startup
(defensive move).

In addition, implement a fully local avatar system, which is used as a fallback
when loading a remote avatar fails. It can also be forced using a prop.

The fully local avatars use a user icon as a mask and apply a background color
qhich is picked by hashing the URI passed to the avatar. If no URI is passed a
random color is chosen.

A grace period of 1 second is also implemented so a default local avatar will be
rendered if an Avatar component is mounted but has no URI. If a URI is specified
later on, it will be loaded and displayed. In case loading the remote avatar
fails, the locally generated one will be used.

Dames en heren, welcome to Jitsi Meet SDK for Android, the Jitsi Meet library
for Android.

The Jitsi Meet SDK encapsulates React Native and all the dependencies Jitsi
Meet has so other aopplications can integrate it easily.

Unlike iOS, creating "fat" libraries is not allways (if at all) possible on
Android, however, effort was put into making the integration as easy as
possible.

While React Native can be embedded in native applications, I don't think it was
designed to be embedded as part of an Android library, hidden away from the
application using it. This surfaced as a number of issues which had to be
addressed specifically due to our use-case:

- Activity lifecycle methods must be linked with the React Native engine, so the
  library provides wrapper methods.
- Custom fonts have to be manually added as assets, since the provided gradle
  script doesn't work properly in a library target.
- The RN packager has to be manually triggered since the gradle script will no
  longer do it for us.

At this stage, the Jitsi Meet application is just a small single activity
application which uses the Jitsi Meet SDK to create a single activity which
represents the entire application. Events and external conference handling are
forthcoming.

PS: Yours truly would like to add that it was a lot more fun to work on the iOS
side of things.

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.

- Use 1 name for 1 abstraction. Instead of useFullScreen and enabled use
  fullScreen.
- Comments are correct English sentences so no double spaces between
  senteces, no capitalization of the work On midsentence.
- Write as little source code as possible if readability is preserved.
- Utilize Facebook's Flow.
- The name of a private function must start with _ and the jsdoc should
  state that the function is private.

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.

As a step toward merging jitsi-meet-react with jitsi-meet to share as
much source code as possible between mobile and Web, merge the part of
jitsi-meet-react's source tree which supports mobile inside the
jitsi-meet source tree and leave jitsi-meet-react's Web support in the
source code revision history but don't have it in master anymore because
it's different from jitsi-meet's Web support. In other words, the two
projects are mechanically merged at the file level and don't really
share source code between mobile and Web.

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.