Add documentation for built-in event-handlers and message broadcasts

[cfgrok]

Currently the only documentation that exists in the wiki for built-in event-handlers or message broadcasts is:

1. The How-Tos page describing Application.cfc integration support that was added in MG 3
2. A brief note under the "name" attribute of the event-handler tag in the XML Reference that describes the "special" behavior of the modelglue.onRequestStart, modelglue.onQueueComplete and modelglue.onRequestEnd event-handlers

Documentation should be added that explicitly describes these three event-handlers, and their corresponding message broadcasts (onRequestStart, onQueueComplete and onRequestEnd).

It may make sense to combine this with the aforementioned Application.cfc integration page, perhaps renaming it to something more descriptive of all the built-in events/messages that are intended for use by end users.