Beginning of Android intents handling

I'm headed out of town, so I figured I'd go ahead and get some eyes on this and let some people start playing with it.

This is the start of cleanly handling intents on Android, so we can avoid a huge mess of jni as we start to do more.

Here, we add a new bridge that lets us call native from Java, which is much cleaner for more android-y interfaces like listeners and broadcasters.

Next step is to add functionality for waiting on messages, callbacks, etc, and to remove our jni code for sending intents in favor of adding it here.