feat(android): get instanceId

[m1ga]

Use

FirebaseCore.addEventListener("instanceId", function(e) {
	console.log("instanceId: " + e.value);
})
FirebaseCore.getInstanceId();

to receive the installation ID.

https://firebase.google.com/docs/projects/manage-installations#java_2 (iOS version would be there too).

Don't know if we already have this in a different module or not :smile:

firebase.core-android-6.1.4.zip

[hansemannn]

We actually have it in Firebase Analytics (Android, iOS), but if it makes sense, we can move it to here as well.