Add properties to AlarmValue

[acaproni]

The AlarmValue is the value of HIO of type ALARM. In the actual implementation an alarm can be either set or cleared. When it is set, it could be useful to have some more information for example if an alarm is raised because the value of a temperature is greater then a given threshold, it could be useful to have the actual value of the temperature associated to the AlarmValue itself.

Note that the value of the temperature, for example, is available as a monitor point (A HIO in input to the ACE that ran the TF) so it is possible to get its value from there but:

• the value of the temperature associated to the AlarmValue is the value atthe time of runing the TF that can be different from the actual value of the HIO
• the displaying of the alarm state (a GUI for example) can avoid to access an HIO if the relevant information are already present in the AlarmValue