Asynchronous status reporting - keeps workers from blocking on UI status reporting

Hi all, this is a proposed change that makes the default status service use asynchronous messaging for status events. I experienced a deadlock when a worker thread reported a status after grabbing a lock while the UI thread was repainting. The UI thread blocked when it tried to get the worker thread's locked object and ImageJ deadlocked because the worker thread blocked while waiting for the status event to be handled by the UI thread.

This limits the problem somewhat.