Classes used to define event handling in the microcontainer. The mechanism is similar to that of JMX notifications,
where by one can create a KernelEventListener and register and unregister it with the
KernelEventManager. Events that the KernelEventListener are interested in can be furter narrowed
down by implementing a KernelEventFilter. The events are in the form of KernelEvent implementations,
and emitted by a KernelEventEmitter.