Improved the GN4 alerting system.

1.When the alerting system is down because of an error, then the 'alert reconnecting' suffix is added to the windows title. Note that, in this case, the client tries to reconnect to the alerting server every 5 seconds.

2.An alerting system's exception can be read using the 'ShowLastException' script method.

3.In page designer when an alert for a layer or page change is received, GN4 refreshes only the page the alert belongs to

4.Added the alerts of texts in article designer (the alerts of geometries were already managed). This allows to manage also the changes of texts that don't update the geometry.

5.Only the changed text is refreshed when a 'text modified' alert is received.

6.Changing the article's name now updates correctly the article treeview.

7.Alerts started from Txt Designer in Fred4 are now correctly processed by Page Designer in the same app.

8.Now Fred4 refreshes correctly the page when another client imports ads on the same layer.