Enhance BAR Preview information to include the estimated size of the restore.

Having recently converted from Networker Legato we have found a number of features that are lacking in Netbackup, one of the more important ones (for us) is a lack of information regarding the amount data that is selected for restore.

Being told how much space is required for any given restore is a feature that we relied heavily on in the past and Netbackup not telling us, or  having a way that it can be quickly and easily calculated, is causing us a real headache.