Knowledge is power, man!

The config.js cache predates the feature base/known-domains.
Technically, it's also able to recall more domains that the feature
recent-list can (because the latter limits its entries).

If multiple JitsiMeetView instances are created (not necessarily
existing at once), it's possible to hit a TypeError when reading the
React Component props of the currently mounted App. Anyway, in certain
places we're already protecting against that out of abundance of caution
so it makes no sense to not protect everywhere.

* Button conditionally shown based on if the feature is enabled and available
* Hooks for launching the invite UI (delegates to the native layer)
* Hooks for using the search and dial out checks from the native layer (calls back into JS)
* Hooks for handling sending invites and passing any failures back to the native layer
* Android and iOS handling for those hooks

Author: Ryan Peck <rpeck@atlassian.com>
Author: Eric Brynsvold <ebrynsvold@atlassian.com>

* feat(Deeplinking): Implement for web.

* ref(unsupported_browser): Move the mobile version to deeplinking feature

* feat(deeplinking_mobile): Redesign.

* fix(deeplinking): Use interface.NATIVE_APP_NAME.

* feat(dial_in_summary): Add the PIN to the number link.

* fix(deep_linking): Handle use case when there isn't deep linking image.

* fix(deep_linking): css

* fix(deep_linking): deeplink -> "deep linking"

* fix(deeplinking_css): Remove position: fixed

* docs(deeplinking): Add comment for the openWebApp action.

On Android the files will be copied to the assets/sounds directory of
the SDK bundle on build time. To play the "asset:/" prefix has to be
used to locate the files correctly.

On iOS each sound file must be added to the SDK's Xcode project in order
to be bundled correctly. To playback we need to know the path of the SDK
bundle which is now exposed by the AppInfo iOS module.

* fix(welcome-page): modify styling for narrow screens

* squash: fix autoscrolling on mobile safari

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.

This only works automatically on Android >= 8. On other platforms / versions, it
relies on the SDK user on implementing a "reduced UI" mode and reacting to the
"request PIP" delegate method.

It's detected based on a size threshold.

We started on the way to responsive UI and its design with aspect ratio
and keeping the filmstrip on the short side of the app's visible
rectangle.

Shortly, we're going to introduce reduced UI for Picture-in-Picture. And
that's where we'll need another dimensions-based detector akin to the
aspect ratio detector.

While the AspectRatioDetector, the up-and-coming ReducedUIDetector, and
their base DimensionsDetector are definitely separate abstractions and
implementations not mixed for the purposes of easy extensibility and
maintenance, the three of them are our building blocks on top of which
we'll build our responsive UI.

[RN] Fix PR feedbacks, write persistency docs

They will be stored in redux and the PageReloadOverlay will be displayed.

Note that this commit also introduces a subtle (and yet important!) change:
the location URL is now always set, regardless of the configuration loading or
not. This is needed in order for the retry logic to pick it up.

On web Conference is pretty much all there is, but on mobile we have the welcome
page and the blank page. If we fail to load config.js, for example we will still
be in the welcome page *and* we want to show an error overlay.

Prepares for the latest eslint & flow-related npm packages which cause
these errors.

Adds the ability to detect app area's aspect ratio on react-native
through the features/base/aspect-ratio.

Makes conference, filmstrip and toolbox react to the aspect ratio
changes and display filmstrip on the shorter side of the screen.

e09949be9f introduced the dark theme globally, but
it only applies to web, so move the logic to App.web.js

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.

This commit adds initial support for CallKit on supported platforms: iOS >= 10.

Since the call flow in Jitsi Meet is basically making outgoing calls, only
outgoing call support is currently handled via CallKit.

Features:
 - "Green bar" when in a call.
 - Native CallKit view when tapping on the call label on the lock screen.
 - Support for audio muting from the native CallKit view.
 - Support for recent calls (audio-only calls logged as Audio calls, others show
   as Video calls).
 - Call display name is room name.
 - Graceful downgrade on systems without CallKit support.

Limitations:
 - Native CallKit view cannot be shown for audio-only calls (this is a CallKit
   limitaion).
 - The video button in the CallKit view will start a new video call to the same
   room, and terminate the previous one.
 - No support for call hold.

Prepare for React 16.

The basic indicator is extracted into a LoadingIndicator component,
which then NetworkActivityIndicator displays (or not) based on network
activity.