quick_frontend (app, widget): CagouWidget.onSelected is called when the widget is selected:

A property is now used to manage `selected_widget` in QuickApp, and widget's onSelected
method is called when suitable.

sat_frontends/quick_frontend/quick_widgets.py

@@ -462,3 +462,7 @@ class QuickWidget(object):
             all other value continue deletion
         """
         return True
+
+    def onSelected(self):
+        """Called when host.selected_widget is this instance"""
+        pass