Save active view on the todo panel

Add a configuration option appearance.todoview and use it to
automatically save the currently active todo panel view and restore it
when restarting calcurse.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/ui-todo.c

@@ -327,3 +327,14 @@ void ui_todo_view_prev(void)
 	ui_todo_view--;
 	ui_todo_load_items();
 }
+
+void ui_todo_set_view(int view)
+{
+	ui_todo_view = (view < 0 || view >= TODO_VIEWS) ?
+		       TODO_SHOW_COMPLETED_VIEW : view;
+}
+
+int ui_todo_get_view(void)
+{
+	return (int)ui_todo_view;
+}