JOSS review: model status indicators

[WarmCyan]

There's no explicit indication anywhere for whether the model is seeded or how many remaining labeled points are needed for the model to start running
(make sure to include notification if only I/U points are currently labeled)

[WarmCyan]

Still working on writing tests for this, but a basic text indicator has been added beneath the data manager widget, with text describing required conditions before model begins predicting