Should have the ability to apply a custom event handler

[toddjordan]

Should be able to add a function to a field or a group of fields, that is invoked on a specific named event to allow for the form to be updated appropriately by the function when the event occurs.

Event handlers will go in forms/events/* and must implement a function that handles an event that takes free form arguments. It must also provide the name of the event its interested in.