Rearrange the ToolbarButtons in the secondary Toolbar in order to mostly
group the media-related ones such as the AudioRouteButton, the
switchCamera button, and the audio-only mode button.

Due to the difference in nature, the iOS and Android implementations are
completely different:

iOS: MPVolumeView is used, which allows us to place a button which will launch a
native route picker provided by iOS itself. This view is different depending on
the iOS version, with the iOS 11 version being more complete.

Android: A completely custom component is used, which displays a bottom sheet
with the device categories, not devices individually. This is akin to the sheet
in the builtin dialer.

This commit adds extra actions/Redux state to be able to deal with
the GUM operation being in progress. There will be early local track
stub in the Redux state for any a local track for which GUM has been
called, but not completed yet.

Local track is considered valid only after TRACK_ADDED event when it
will have JitsiLocalTrack instance set.

The intention was to override 'this' argument of 'Error.toString'.

Fallback to the room name otherwise. This allows us to have better entries in
the phone history.

HIDE_DIALOG happens between WILL_JOIN and JOINED so get the joining conference
from the state instead of the action.

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.

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

In certain scenarios we do need to import files instead of features but
even then it is our coding style to not write the file extension.

The error is stored in the redux store in base/config so other components can
consult it. It is also broadcasted as a new event in the external API for the
SDK.

I'm not saying that the two commits in question were wrong or worse than
what I'm offering. Anyway, I think what I'm offering brings:

* Compliance with expectations i.e. the middleware doesn't compute the
next state from the current state, the reducer does;

* Clarity and/or simplicity i.e. there's no global variable (reqIndex),
there's no need for the term "index" (a.k.a "reqIndex") in the redux
store.

* By renaming net-interceptor to network-activity feels like it's
preparing the feature to implement a NetworkActivityIndicator React
Component which will take on more of the knowledge about the specifics
of what is the network activity redux state exactly, is it maintained by
interception or some other mechanism, and abstracts it in the feature
itself allowing outsiders to merely render a React Component.

Works only for XHR requests, which is the only network request mobile performs
(WebRTC traffic aside). The fetch API is implemented on top of XHR, so that's
covered too.

Requests are kept in the redux store until they complete, at which point they
are removed.

Simplify the code by using a bitfied instead of a couple of boolean flags. This
allows us to mute the video from multiple places and only make the unmute
effective once they have all unmuted.

Alas, this cannot be applied to the web without a massive refactor, because it
uses the track muted state as the source of truth instead of the media state.

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.

The value of inviteURL is derived from locationURL by removing the hash
and query/search params in order to make it fit for display and/or
public purposes. The Jitsi Meet SDK consumers do not fall into that
category and our intention is to provide them with the URL they used
with JitsiMeetView.openURL(URL) anyway.

Also rewrites to remove repetition. I'm not saying the new source code
is better really but at least I got to examine it and comment on some of
its weaknesses.

The current implementation doesn't use the API and Transport modules. This is
due to the fact that they are too tied to APP at the moment, which is web only.

Once API is refactored and moved into the Redux store this will be adjusted,
though it's unlikely that the lowest level React Native module (ExternalAPI)
changes drastically.

This commit also introduces a stopgap limitation of only allowing a single
instance for JitsiMeetView objects on both Android and iOS. React Native doesn't
really play well with having multiple instances of the same modules on the same
bridge, since they behave a bit like singletons. Even if we were to use multiple
bridges, some features depend on system-level global state, such as the
AVAudioSession mode or Android's immersive mode. Further attempts will be made
at lifting this limitation in the future, though.

When a dialog is opened on Android, full-screen mode is exited but we (the app)
know nothing about this. Make sure we re-enter full-screen mode once a dialog is
closed, if the conditions to be in such mode are still met.

When the audio-only mode is enabled, turn on the proximity sensor to dim the
screen and disable touch controls when there is an object nearby.

The behavior can be triggered with the toggleAudioOnly action, which is
currently fired with a button.

The following aspects of the conference will change when in audio only mode:

- local video is muted
- last N is set to 0 (effectively muting remote video)
- full-screen mode is exited
- audio mode is set to "audio chat" (default output is the earpiece)
- the wake lock is disengaged

One aspect not handled in this patch is disabling the video mute button while in
audio only mode. The user should not be able to turn back video on in that case.

This is in preparation for an upcoming "audio only mode" feature. Setting last N
will also be required for it, so this patch factors out the action and makes it
public so other modules can reuse it.

In addition, if the value is set to undefined the configured default value (or
-1 if absent) is picked.