This reverts commit c9a29153dd.

Now that react-native-webrtc supports the permissions system in 23, use it since
it provides a more pleasant experience to users.

In addition, fix a bug in the previous code: the React Native view must be
loaded after we have acquired the permission to draw on top of other apps,
otherwise our app may crash while we accept the permission, since React may try
to draw.

API level 22 is below 23 (aka Marshmallow), which included an overhaul in the
permissions system. React Native recommends 22 (it's the default when you create
a new app) and there have been reports when set higher [0] and [1].

This also fixes a critical bug, wherein Jitsi Meet wouldn't request permissions
for the camera and microphone.

Last, this change also allows us to get rid of the overlay checking code,
because it was only needed for API level 23 or higher.

[0]: https://github.com/facebook/react-native/pull/10479
[1]: https://github.com/facebook/react-native/issues/10587

Also expose this in the native SDKs.

Copy it from the main fonts directory instead.

Changing the props from native (Java) code was only added in 0.45, so add a
workaround until we get to updating our React Native dependency.

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.

Dames en heren, welcome to Jitsi Meet SDK for Android, the Jitsi Meet library
for Android.

The Jitsi Meet SDK encapsulates React Native and all the dependencies Jitsi
Meet has so other aopplications can integrate it easily.

Unlike iOS, creating "fat" libraries is not allways (if at all) possible on
Android, however, effort was put into making the integration as easy as
possible.

While React Native can be embedded in native applications, I don't think it was
designed to be embedded as part of an Android library, 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:

- Activity lifecycle methods must be linked with the React Native engine, so the
  library provides wrapper methods.
- Custom fonts have to be manually added as assets, since the provided gradle
  script doesn't work properly in a library target.
- The RN packager has to be manually triggered since the gradle script will no
  longer do it for us.

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

PS: Yours truly would like to add that it was a lot more fun to work on the iOS
side of things.