Prioritize dialog: allow adding multiple criteria at once

Adding criteria to the prioritizations list one-by-one can be tedious.
This commit enables extended selection in the criteria list and
implements adding multiple items. Multiple criteria can be selected with
conventional methods, such as holding down Ctrl or Shift keys and
clicking the items or holding down the left mouse button and hovering
the cursor over the list. All items also can be selected with Ctrl+A.

Signed-off-by: Sergey Zhuravlevich <sergey@zhur.xyz>

qt/prioritize_dialog.py

@@ -102,6 +102,7 @@ class PrioritizeDialog(QDialog):
         self.promptLabel.setWordWrap(True)
         self.categoryCombobox = QComboBox()
         self.criteriaListView = QListView()
+        self.criteriaListView.setSelectionMode(QAbstractItemView.ExtendedSelection)
         self.addCriteriaButton = QPushButton(
             self.style().standardIcon(QStyle.SP_ArrowRight), ""
         )