This PR changes the logic for connecting / disconnecting conferences. Instead of
doing it in mount / unmount events from the Conference component, it moves the
logic to the appNavigatee action.

This fixes a regression introduced in 774c5ecd when trying to make sure the
conference terminated event is always sent.

By moving the logic to appNavigate we no longer depend on side-effects for
connecting / disconnecting, and the code should be more maintainable moving
forward.

An improvement to this is the concept of sessions, which, while not tackled
here, was taken into consideration.

Dear reader, I'm not proud at all of what you are about to read, but sometimes
life just gives you lemons, so enjoy some lemonade!

Joining a conference implies first creating the XMPP connection and then joining
the MUC. It's very possible the XMPP connection was made but there was no chance
for the conference to be created.

This patch fixes this case by artificially genrating a conference terminated
event in such case. In order to have all the necessary knowledge for this event
to be sent the connection now keeps track of the conference that runs it.

In addition, there is an even more obscure corner case: it's not impossible to
try to disconnect when there is not even a connection. This was fixed by
creating a fake disconnect event. Alas the location URL is lost at this point,
but it's better than nothing I guess.

🔥🔥🔥

Using anything non-serializable for action types is discouraged:
https://redux.js.org/faq/actions#actions

In fact, this is the Flow definition for dispatching actions:

declare export type DispatchAPI<A> = (action: A) => A;
declare export type Dispatch<A: { type: $Subtype<string> }> = DispatchAPI<A>;

Note how the `type` field is defined as a subtype of string, which Symbol isn’t.

If a relative BOSH URL is found (as docker-jitsi-meet does) construct a full URL
based on the location URL and context root.

Also remove some default options since we need the config file anyway, so I see
no point in doing the extra work.

Unfortunately, as the Jitsi Meet development evolved the routing mechanism
became more complex and thre logic ended up spread across multiple parts of the
codebase, which made it hard to follow and extend.

This change aims to fix that by rewriting the routing logic and centralizing it
in (pretty much) a single place, with no implicit inter-dependencies.

In order to arrive there, however, some extra changes were needed, which were
not caught early enough and are thus part of this change:

- JitsiMeetJS initialization is now synchronous: there is nothing async about
  it, and the only async requirement (Temasys support) was lifted. See [0].
- WebRTC support can be detected early: building on top of the above, WebRTC
  support can now be detected immediately, so take advantage of this to simplify
  how we handle unsupported browsers. See [0].

The new router takes decissions based on the Redux state at the time of
invocation. A route can be represented by either a component or a URl reference,
with the latter taking precedence. On mobile, obviously, there is no concept of
URL reference so routing is based solely on components.

[0]: https://github.com/jitsi/lib-jitsi-meet/pull/779

* fix(connection): reload immediately on possible split-brain

There isn't an explicit way to know when a split brain
scenario has happened. It is assumed it arises when an
"item-not-found" connection error is encountered early
on in the conference. So, store when a connection has
happened so it be calculated how much time has
elapsed and if the threshold has not been exceeded
then do an immediate reload of the app instead of
showing the overlay with a reload timer.

* squash: rename isItemNotFoundError -> isShardChangedError

Currently the listeners for disconnected and failed connection events
are unsubscribed as soon as the connection is established, so
the CONNECTION_DISCONNECTED is never triggered which would clear the
'connection' field. This commit will clear the 'connection' state on
CONNECTION_WILL_CONNECT. It's needed anyway given that there's no
guarantee on when and if the async disconnect operation will finish.

One issue caused by the 'connection' not cleared was that
CONNECTION_FAILED was not reduced correctly and the reload screen was
not displayed for the following scenario:
1. Join and leave any working conference.
2. Turn off network connectivity on the device.
3. Wait for CONNECTION_FAILED. The reload screen will not be displayed,
   because CONNECTION_FAILED is not reduced correctly, because the old
   'connection' value is still there.

Try to use the getCurrentConference function wherever the indention is
to check for the current conference.

After the connection is established, it can either be properly disconnected or
fail. We need to make sure to be listening for events for either.

Because there are multiple reasons on why a conference.leave() may fail
it's helpful to know if and why it happened.

Introduce ConnectionFailedError type.

Delay the CONFERENCE_FAILED event until the user cancels the login
dialog using the 'recoverable' event flag.

In order to be able to add analytics to the deep-linking pages the
lib-jitsi-meet initialization has been moved so it happens earlier.

The introduced `initPromise` will eventually disappear, once conference is
migrated into React and / or support for Temasys is dropped. At that stage, it
can be turned into a sync function which all platforms share.

* Handles connection failed event details (passing them to analytics).

* Fixing comments.

* Updates depending versions to be able to test.

* Fixing comments.

* Fixes wrong jsdoc.

Properly handle errors while connecting or joining a conference. Prior to this
patch, only errors on established conferences / connections were saved to the
redux store.

Initializing UI features, like keyboard shortcuts, by chaining
onto APP.conference.init is not safe because init can fail,
skipping the initializing of UI features. This can happen when
the room is locked and then a failure event is dispatched into
middleware. I couldn't find a place to properly chain onto
in the APP.conference.init promise chain, primarily due
to the flow continued within middleware, so instead I
leveraged an existing listener for CONFERENCE_JOINED.

Will override email, display name and avatar URL with the values
provided in 'context.user' structure of the JWT token.

Settings will no longer be used to retrieve local display name,
email and avatar URL. Now those values will be obtained from
the /features/base/participants Redux state.

fix(jwt/middleware): use const for default name

fix: wrong default display name on web

ref(base/participants): remove getDisplayName functions

ref(jwt): do not accept unknown user fields

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.

Gradually, we exploded the error of CONNECTION_FAILED in multiple
redux state properties. The explosion makes maintenance harder because
the properties have to be updated in sync. Collect them in an object
resembling an Error instance.

Do not show the 'Password is incorrect' message when the LoginDialog
opens for the first time.

In order to support XMPP authentication, we'll need the message
accompanying the error and carried by lib-jitsi-meet's
CONFERENCE_FAILED in the redux store. We already carry the message in
the redux action and we've got the error in the redux store.

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.

Keep track of the connection and conference objects so we can leave and / or
disconnect early, before the connection is established or the conference joined.