We need to improve the events dispatching system so that it's more Swing like (ie events and listeners are more fine grained - IssueAssignedEvent and AssignIssueListener).

This would allow us much more flexibility in the event dispatching / listening system.

Also we need to ensure the order of listeners, make listeners installed / uninstalled, allow you to install more than one of a given listener and make sure system listeners occur in the right order.