The welcomePageEnabled and pictureInPictureEnabled props on mobile have been
converted to feature flags.

Consolidate all failure cases into a single one: CONFERENCE_TERMINATED. If the
conference ended gracefully no error indicator will be present, otherwise there
will be.

- cleanup
- API simplification (single loadURL method)
- JitsiMeet singleton for linking helpers and globals
- Linking moved to app

We are going to implement the invite dialog *inside* the SDK, so there is no
need to have all this machinery anymore.

This is mostly implemented in the app, with the needed support in the SDK. Since
the app needs to donate intents and deal with creating NSUserActivity objects it
doesn't feel right to do this in a library. Instead, we donate the intents from
the app, but the SDK is ready to extract conference URLs from any intent which
was registered as a conference activity.

This also opens the door for eventually adding Handoff support.

If the beginAddPeople delegate method is implemented, and they haven't been
explicitly set to NO, they willbe YES.

We just call the parent class' method, so just get rid of it.

JitsiMeetViewListener is an integral part of the public API of Jitsi
Meet SDK for Android. Utilize it in the Debug configuration of the Jitsi
Meet app for Android in order to increase (1) awareness of API breakages
and (2) API coverage.

The same goes for JitsiMeetViewDelegate in Jitsi Meet SDK and app for
iOS.

1. Aligns the project structure of Jitsi Meet SDK for iOS with that for
   Android for better comprehension.

2. The command `react-native run-ios` uses the last Xcode project or
   workspace in the list of these sorted in alphabetical order. Which
   limits our freedom in naming. Thus having only an Xcode project in
   the root directory of the iOS project structure gives us back the
   freedom in naming.

3. Allows the Podspec to work for the app project in addition to the sdk
   project because we need Crashlytics in the app which is integrated
   via Cocoapods as well.

4. Further removes references to JitsiKit in the source code for the
   sake of consistent naming.

Ladies and gentlemen, allow me to introduce you to Jitsi Meet SDK for iOS, the
mobile SDK which powers Jitsi Meet.

The goal is to encapsulate the entire React Native app into a framework / SDK
and offer an API for native (ObjC or Swift) applications to embed the Jitsi
conferencing experience.

While React Native can be embedded in native applications, I don't think it was
designed to be embedded as part of a framework, hidden away from the application
using it. This surfaced as a number of issues which had to be addressed
specifically due to our use-case:

- Universal / deep linking needed to be wrapped to avoid the embedding app from
  linking with RN.
- The bundle URL had to be manually constructed, since RN considers that all
  resources are in the main bundle, but in case of a framework that is not the
  case.
- Custom fonts had to be manually loaded, since UIAppFonts doesn't work on the
  framework's Info.plist file.
- The RN packager has to be manually triggered since the React project will no
  longer do it for us.
- Custom App Transport Security rules were added since the builtin way to do it
  modifies the framework's Info.plist, which is useless in this case.

At this stage, the Jitsi Meet application is just a small single view
application which uses the Jitsi Meet SDK to create a single view which
represents the entire application. Events and external conference handling are
forthcoming.