The visibility of the toolbar can be toggled by interacting with the main screen.
This change allows the toolbar to be configured to be 'always visible'. This voids
the 'toggle' functionality.

As part of the work on fixing the problem with the multiplying
thumbnails, we've associated remote participant w/ JitsiConference.
However, there are periods of time when multiple JitsiConferences are in
the redux state (and that period is going to be shorted by
StateListenerRegistry). In order to give more control to the feature
base/participants, reduce the occurrences of direct access to the
features/base/participants redux state and utilize the feature's
existing read access functions. Which will allow us in the future to
enhance these functions to access participants which are relevant to the
current conference of interest to the user only.

Show it if we are the only participant, and hide it the moment someone else
joins the conference.

Since the main conference container is no longer "clickable" there must
be a way for clicking on the "large video". A clickable TestHint nested
in ParticipantView makes it easier for dealing with the fact that the
click handler is not always on the same component (required for the
pinch and zoom feature to work correctly).

Be explciit about the appearance we desire, since each mounted StaturBar
component will override the existing values. In this case, the problem was
caused because the default on iOS is dark, whereas it's light on Android.

Set it to light so it works consistently across both, which is what we want.

Adds TestConnectionInfo component which exposes some internal app state
to the jitsi-meet-torture through the UI accessibility layer. This
component will render only if config.testing.testMode is set to true.

TouchableWithoutFeedback and TouchableHighlight interfere with the
implementation of 'pinch to zoom' to come. We prepare for it by driving
the onClick/onPress handler(s) out of Conference, through LargeVideo and
ParticipantView into Video itself where the bulk of 'pinch to zoom' will
be implemented.

In preparation for "pinch to zoom" support in desktop streams on mobile, make
certain Views not intervene in touch event handling. While the modification is
necessary for "pinch to zoom" which is coming later, it really makes sense for
the modified Views to not be involved in touching because they're used to aid
layout and/or animations and are to behave to the user as if they're not there.

It's designed to cover a container and give it a "tint" by using a color and
opacity.

It's not supposed to go on top of everything, like an error would. It's tied to
a conference, so render it outside of the OverlayContainer.

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.

Adds more accessibility labels required for mobile automated testing.

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.

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.

When do we need tracks?

- Welcome page (only the video track)
- Conference (depends if starting with audio / video muted is requested)

When do we need to destroy the tracks?

- When we are not in a conference and there is no welcome page

In order to accommodate all the above use cases, a new component is introduced:
BlankWelcomePage. Its purpose is to take the place of the welcome page when it
is disabled. When this component is mounted local tracks are destroyed.

Analogously, a video track is created when the (real) welcome page is created,
and all the desired tracks are created then the Conference component is created.
What are desired tracks? These are the tracks we'd like to use for the
conference that is about to happen. By default both audio and video are desired.
It's possible, however, the user requested to start the call with no
video/audio, in which case it's muted in base/media and a track is not created.

The first time the app starts (with the welcome page) it will request permission
for video only, since there is no need for audio in the welcome page. Later,
when a conference is joined permission for audio will be requested when an audio
track is to be created. The audio track is not destroyed when the conference
ends. Yours truly thinks this is not needed since it's a stopped track which is
not using system resources.

The functions need not return anything, or it will be dispatched as another
action.

The files styles.js are used (pretty much) on React Native only and each
of them exports 1 name. Export it as default to cut down on source code.

We've had Filmstrip & LargeVideo React Components on mobile/React Native
from the start. We didn't have them on Web (because the rewrite in React
is not complete yet). However, that led to differences in the React
Component Conference on Web and mobile. In an effort to get closer to
merging the React Component Conference on Web and mobile, introduce the
React Components Filmstrip & LargeVideo on Web even if a minimal
render-only form at this time.

We seemed to be using the names "film strip" and "filmstrip" (and,
consequently, their source code-conscious forms such as film-strip,
FilmStrip, etc.) In order to comply with our coding style which requires
a consistent one name for a given abstraction, choose one name and
rename the uses of the other name.

Wikipedia has a definition of a "filmstrip", I couldn't find a "film
strip". I guess our abstraction can be seen as what's described there.
When I google "film strip", I get results about "filmstrip" at the top.
That's why I chose "filmstrip".

Certain uses of "film strip" such as interfaceConfig.filmStripOnly and
in the external API I left untouched in an attempt to preserve
compatibility.

I wasn't sure whether CSS was tangled in compatibility so I made a
choice and renamed there was well.

Moves native dialogs to use dialog container. Implements native Dialog that uses react native Prompt.