[REVIEW] Allow caller to specify no-arg controller method as an event handler

[Greg Brown]

This is a review request for RT-18229:

http://javafx-jira.kenai.com/browse/RT-18229

In JavaFX 2.0, controller-based event handlers must adhere to the method signature defined by an event handler; in other words, they must accept a single argument of a type that extends Event and return void. This change lifts the argument restriction, making it possible to write a controller event handler that takes no arguments.