Notifications support

[wsargent]

It'd be nice if an MBean could specify an annotation that would add an MBeanNotificationInfo to an attribute or operation:

• https://docs.oracle.com/javase/8/docs/api/javax/management/MBeanNotificationInfo.html
• https://docs.oracle.com/javase/tutorial/jmx/notifs/index.html
• https://docs.oracle.com/javase/8/docs/technotes/guides/jmx/JMX_1_4_specification.pdf 2.5 JMX Notification Model