Add a Jenkins job to build the Android application

In order to build an APK, deploy it to the Google Play Store and allow beta testing of the Android app.

Let's use a "Pipeline script from SCM" just as in https://qa.nuxeo.org/jenkins/job/Client/job/nuxeo-automation-php-client-master/configure.

Just as in https://github.com/nuxeo/nuxeo-automation-php-client/blob/2.0-rewrite/Jenkinsfile, we will probably:
1. Start by pulling a Linux basic docker image with Java

docker.image('quay.io/nuxeo/nuxeo-qaimage-java').pull()

2. Build it with everything we need for the Android build: Android SDK, gradle, node, npm, fastlane, etc. using a Dockerfile:

docker.build('nuxeo-qaimage-android', 'docker/android')

3. Run the deployment script inside it:

.inside {
  # Deployment tasks
}

Let's check the docker hub, there might be an existing Android image that would suit our needs.

Check NXMOB-220 about the iOS deployment scripts refactored with Pipeline.