C++ Wrapper for BroadcastReceiver

BroadcastReceiver's [onReceive method](https://developer.android.com/reference/android/content/BroadcastReceiver?hl=en#onReceive(android.content.Context,%20android.content.Intent)) is used to receive broadcast Intents after [registration for them](https://developer.android.com/reference/android/content/Context?hl=en#registerReceiver(android.content.BroadcastReceiver,%20android.content.IntentFilter)), but the method is abstract.

It appears that, presently, one needs a Java class to receive broadcast Intents (that it can't be done through JNI), although I am not certain of this. It would be great if there were a way to receive broadcast Intents from native code.

Note that adding [java.beans.EventHandler](https://docs.oracle.com/javase/7/docs/api/java/beans/EventHandler.html) to the Android API might provide for more workarounds to things like this, not certain.

Start with the linked BroadcastReceiver.onReceive and Context.registerReceiver documentation, then investigate whether JNI can expose broadcast reception to native code without a Java receiver. Done would require a clearly supported native approach or a documented conclusion that the request needs a broader Android API design.

Written by the indexing model from the issue text.