Added GUI dialog instead of command line output for empty workload.
Renamed NoDataException to NoWorkUnitExecption.
WxWidgetTestCases now unsub from all events during setup.
Converted EmptyWorkloadModelTest into an application level test that
incorporates the model and the controller and makes sure they call the 
view.
Minor dialog message fix.
If a local file already exists in the temp directory for the SyncingVOFile,
it is first deleted to avoid its contents ending up in the VOFile.