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

* feat(audio-only): be able to lock a browser into capturing audio only

* squash: try to make string more clear about audio only support

* squash: final strings

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.

Prepare for React 16.

Filmstrip only mode displays a device selection dialog that
does not have access to the redux/connect. However, the current
VideoTrack extends from AbstractVideoTrack, which assumes a
redux connection. The fix is to move video display logic into
a separate component and have device selection use that, while
the existing VideoTrack remains connected to redux but
uses the new video display component.

This is only desired when the unmuting action took place due to a manual user
intervention or the audio-only mode being disengaged.

* ref: video muted state

Get rid of 'videoMuted' flag in conference.js

* ref: audio muted state

Get rid of 'audioMuted' flag in conference.js

* fix(conference.js|API): early audio/video muted updates

* ref(conference.js): rename isVideoMuted

Rename isVideoMuted to isLocalVideoMuted to be consistent with
isLocalAudioMuted.

* doc|style(conference.js): comments and space after if

* ref: move 'setTrackMuted' to functions

* fix(tracks/middleware): no-lonely-if

* ref(features/toolbox): get rid of last argument

* ref(defaultToolbarButtons): rename var

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.

Make toolbar's microphone button enabled whenever there are any
'audioinput' devices available and allow to add audio during
the conference even if microphone permissions were denied on startup.

Because on web video track is stored both in redux and in 'localVideo'
field, video is attempted to be unmuted twice when turning off the audio
only mode. This will crash the app with 'unmute operation is already in
progress'. This commit will prevent from taking action from the web
world if the video track already exists and will make the redux side
rollback unmuted status in case unmute fails.

* feat(local-video): convert to react

- Create a VideoTrack component for displaying a video element.
  This mirrors native also having a VideoTrack component.
- The VideoTrack component does not let React update it to prevent
  the video element from re-rendering, which could cause flickers
  and would not work with temasys's overriding of the video element.
- VideoTrack extends AbstractVideoTrack to mirror native
  implementation and to get the dispatch of the onplaying event.
- Remove the onclick handler on the video element. Honestly, I
  didn't get it to work, and did not try, but it is also unnecessary
  because another handler already exists on the video wrapper.

* ref(device-selection): VideoInputPreview uses VideoTrack to show video

* squash into conversion: change css selectors

* squash into conversion: mix in abstract props

* squash into conversion: change shouldComponentUpdate check

* squash: update comment about why triggerOnPlayingUpdate is used

Dynamically enables/disables the toolbar video button. Prior to that
commit if we would start with no video there would be no way to enable
it later on.

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.

Introduce certain React Components which may be used to write
cross-platform source code such as Audio like Web's audio, Container
like Web's div, Text like Web's p, etc.

It's now natively supported:
https://github.com/oney/react-native-webrtc/pull/244

Use the curstom _switchCamera API provided by react-native-webrtc to toggle the
camera instead of destroying the current track and creating a new one.

_switchCamera is implemented at a low level, so the track perceives no changes,
thus being a lot faster and less involved since the capturer doesn't need to be
destroyed and re-created.

In addition, don't mirror the video for the back camera.

Ref: https://github.com/oney/react-native-webrtc/pull/235

Until we make a decision on access modifier hints and adopt a respective
coding style, consistency is king.

React Native provides Platform.

Redux actions which represent "commands" should be imperative, and those
representing events should use the past tense.