Fix bug in RegisteredEventListener.

The bug caused the constructor of RegisteredEventListener
to not detect that an event monitoring method was unsuitable.
Fix link error in javadoc comments in Real.

The javadoc linked to a method that did not exist.
Add EventMonitor to the project.

The EventMonitor annotation is used to indicate methods that are
to be notified of the outcome of events. These methods receive
the Event object that was fired as well as a Result value
representing the outcome of the action.
Add RegisteredEventMonitor to the project.

This class wraps EventMonitor tagged methods to make it easy to
notify monitors.