Recursively set lifecycle listeners

I'm wondering if it's possible to achieve the behavior of setting a `Controller.LifecycleListener` that gets set on a router to be attached to each controllers' child routers. Doesn't seem like it's possible.

The question arises from the ability to do so on fragments via `FragmentManager#registerFragmentLifecycleCallbacks(FragmentLifecycleCallbacks cb, boolean recursive`.

So I guess in conductor it would look something like `router.addChangeListener(changeListener, true)`

I think it could be useful for conductor to support something like this.

Thoughts?

Start by reading Controller.LifecycleListener and the router listener API, especially the proposed router.addChangeListener(changeListener, true) behavior. Compare it with FragmentManager#registerFragmentLifecycleCallbacks and determine the intended recursive scope. Done means reaching agreement on the API and ensuring a listener registered on a router is attached to each child router.

Written by the indexing model from the issue text.