Added ui_visibility flag

force_bdss/notification_listeners/base_notification_listener_factory.py

 import logging
-from traits.api import ABCHasStrictTraits, Instance, String, provides, Type
+from traits.api import (
+    ABCHasStrictTraits, Instance, String, provides, Type, Bool
+)
 from envisage.plugin import Plugin
 
 from force_bdss.notification_listeners.base_notification_listener import \
@@ -24,6 +26,11 @@ class BaseNotificationListenerFactory(ABCHasStrictTraits):
     #: Name of the factory. User friendly for UI
     name = String()
 
+    #: If the factor should be visible in the UI. Set to false to make it
+    #: invisible. This is normally useful for notification systems that are
+    #: not supposed to be configured by the user.
+    ui_visible = Bool(True)
+
     #: The listener class that must be instantiated. Define this to your
     #: listener class.
     listener_class = Type(BaseNotificationListener)