Adding checks to the alerts for student training.

Fix for ORA-728 and ORA-729 - Alert messages when there are no training examples and alerts when student training is disabled.

Now checking both scenarios before display an alert. Added tests accordingly. 

@wedaly @gradyward 
If this is a pre-condition for just the tests in `oa_edit_listeners`, I'd prefer to enable student training programmatically in `beforeEach()` so it's more visible.