Wrap Listeners for android

[jenow]

What does this PR do ?

Wrap NotificationListener, EventListener and SubscribeListener for android. First make each pure virtual methods abstract for Java.. Then wrap JSON type when needed

How should this be manually tested?

Check if it builds:

docker run --rm -it -v "$(pwd)":/go/src/github.com/kuzzleio/sdk-go android-x86 /custom_build.sh

You can then test it in an android project (for x86 for now). Example of a subscribe with NotificationListener:

Kuzzle k = new Kuzzle("kuzzlehost");
k.getRealtime().subscribe("index", "collection", "{}", new NotificationListener() {
    @Override
    public void onMessage(NotificationResult notificationResult) {
        try {
            Log.e("e", notificationResult.getResult().getContent().toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
});

[codecov-io]

Codecov Report

Merging #195 into 1.x will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##              1.x     #195   +/-   ##
=======================================
  Coverage   89.07%   89.07%           
=======================================
  Files         243      243           
  Lines        4376     4376           
=======================================
  Hits         3898     3898           
  Misses        449      449           
  Partials       29       29

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