The Jitsi Meet app always has at most 1 conference of primary interest.
It may have to juggle with 2 JitsiConference instances at the same time
if 1 is in the process of being left and one is joining/joined. But the
one which is joining or joined (which we call conference in the
features/base/conference redux state) is the one "of interest", the
other one is "clean up". Consequently, the remote participants of the
conference "of interest" are the remote participants "of interest" and
the others are "clean up". In order to reduce the time during which
there may be multiplying remote thumbnails, clean the remote
participants who are no longer "of interest" up.

The commit message of "Associate remote participant w/ JitsiConference
(_JOINED)" explains the motivation for this commit.

Practically, _JOINED and _LEFT combined with "Remove remote participants
who are no longer of interest" should alleviate the problem with
multiplying remote participants to an acceptable level of annoyance.

Technically though, a remote participant cannot be identified by an ID
only. The ID is (somewhat) "unique" in the context of a single
JitsiConference instance. So in order to not have to scratch our heads
over an obscure corner, racing case, it's better to always identify
remote participants by the pair id-conference. Unfortunately, that's a
bit of a high order given the existing source code. So I've implemented
the cases which are the easiest so that new source code written with
participantUpdated is more likely to identify a remote participant with
the pair id-conference.

Additionally, the commit "Reduce direct read access to the
features/base/participants redux state" brings more control back to the
functions of the feature base/participants so that one day we can (if we
choose to) do something like, for example:

If getParticipants is called with a conference, it returns the
participants from features/base/participants who are associated with the
specified conference. If no conference is specified in the function
call, then default to the conference which is the primary focus of the
app at the time of the function call. Added to the above, this should
allow us to further reduce the cases in which we're identifying remote
participants by id only and get us even closer to a more "predictable"
behavior in corner, racing cases.

The plan set in motion here is to associate remote participants with the
JitsiConference instances that created them in order to be able to
remove remote participants when a JitsiConference is no longer the
primary focus of the jitsi-meet app. And that's supposed to alleviate a
problem with multiplying remote thumbnails.

Doing all of the above in a single commit is a bit of a high order. So
I'm splitting the whole into multiple successive commits for the
purposes of observability, comprehension. Each commit is supposed to be
safe even if subsequent commits are not accepted, are reverted,
whatever. Obviously, without the successive commits, a commit may be
"unused".

One of the important pieces of the multiplying remote thumbnails "fix"
offered is removing remote participants who are no longer of interest
i.e. PARTICIPANT_LEFT. But in order for _LEFT to be implemented, _JOINED
must be implemented first.

Doing so in CONFERENCE_JOINED is too late because if we are moderators that
event will come first and we won't know what ID to match it with.

This is safe because our local ID is created early.

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.

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.

* ref(avatars): remove Avatar.js

- Rely on redux getting updated with new participant state
and any calls to getAvatarURL passing in the redux
participant state. This way the state within Avatar.js can
be removed.
- Clean up methods on UI.js. Because all state is in the
store, separate methods for updating the avatar aren't as
necessary. Instead centralize accessing of the avatar for
components outside of redux and centralize the call to
update avatars for non-react components.
- Controversial: cache a participant's avatarURL on the
participant state. Currently the participant's avatarURL
that is generated without jwt (which sets the avatarURL directly)
is not cached. Without cache, there can be many redundant
calls to APP.API.notifyAvatarChanged.

* Leverage middleware timing to diff avatars

One alternative implementation is to leverage middleware's
ability to intercept updates before and after redux has
upated and then compare avatarURLs.

* kill UI.getAvatarUrl

* profile button sets its own avatar url (solves update timing)

* remove calls to updating avatar outside of middleware

* update UI.js doc

* remove left over logic from initial implementation

* try to move local user fallback into selector func

* default to id 'local' in selector

* fix(remote-mute): Moves remote participant mute to react

* fix(translation): Removes unused strings

* [squash] Addressing comments

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+.

* feat(small-video): use InlineDialog for stats and remote menu

- Remove JitsiPopover and use InlineDialog instead.
- Bring the remote menu icon into react.
- Make vertical filmstrip position:fixed so popper (AtlasKit
  dependency) sets InlineDialogs and eventually tooltips to
  position:fixed.

* ref(remote-menu): hook KickButton to redux

* ref(remote-menu): hook MuteButton to redux

* modify padding, toggle dialogs

* pixel push margins to align dialogs, adjust padding of dialogs

* add comment about margin for dialog, add file I forgot

* modify indicator markup so the icon can be moved down while trigger stays at top of toolbar

* feat(display-name): convert to React

- Create a new React Component for displaying and updating display
  names on small videos
- The updating of the Component is defined in the parent class
  SmallVideo, which children will get access to through prototype
  copying
- Create a new actionType and middleware so name changes that occur
  in DisplayName can be propogated to outside redux
- Update the local video's DisplayName when a conference is joined
  or else the component may keep an undefined user id

* squash: query for the container, not the el owned by react

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.