This change makes the MessageQueue use Tasks for sending a Message to each MessageListener. Messages can define their
behavior by setting setSendAsTask(), the default is true. Only MessageStatus and MessageInterruptTasks are still sent on
the Messaging thread to allow for immediate effect.
This change also introduced the class SimpleTask which holds only a single perform() callback to override, for Tasks
that are finished in a single step. The class LambdaTask derives from SimpleTask and allows for passing a lambda as the
perform() callback.
Eberhard Graether
e0ddc67597