Sc209/dropdown menus

• Made a class of the review window in the View
• The drop down menu in the review window has now all ShadowTasks (aka trials) which you can view. Really nice. No functionality yet.
• Fixed some things that were ugly. For example, I added underscores to some variable names. Maybe some argue that all the underscores are ugly, but it makes the file way more readable and now the IDE does not complain any more about spelling mistakes.

umbra/controller.py

@@ -68,6 +68,8 @@ class Controller:
             self._model.change_algorithm(action)
         elif action == 'review':
             self._review_files()
+        elif action == 'cancel_review':
+            self._view.close_review()
 
     def _select_folder(self, type_code='shadow'):
         """Select a folder from which multiple files can be read.