Manage listeners from the kernel

Have the kernel directly manage event listeners. Support namespaced event names.

The kernel will use a private namespace in `branch/collection-events` to send meta events into the application using names that won't conflict with any possible application event name. Additionally, the kernel will need to have direct knowledge of event listeners in order to replicate them correctly.

This is a predecessor to `branch/collection-events`, which uses the event mechanism for the kernel to deliver meta events into the application.

@eric79 , please review.

So, what do you suggest we do immediately?  Does it make sense to use the string for now?  Or is that too much of a backstep wrt the refactoring you suggest?  I am okay with using the string or punting on this for now.